Infertility affects 15% of all couples. Although male infertility factors with reduced semen quality are contributing to about half of all involuntary childlessness, the value of standard semen parameters in prediction of fertility in vivo and choice of proper method for assisted reproduction is limited. In the search for better markers of male fertility, during the last 10 years, assessment of sperm DNA integrity has emerged as a strong new biomarker of semen quality that may have the potential to discriminate between infertile and fertile men. Sperm DNA Fragmentation Index (DFI) as assessed by the flow cytometric Sperm Chromatin Structure Assay (SCSA) can be used for evaluation of sperm chromatin integrity. The biological background for abnormal DFI is not completely known, but clinical data show that DFI above 30% is associated with very low chance for achieving pregnancy in natural way or by insemination, but not in vitro. Already when the DFI is above 20%, the chance of natural pregnancy may be reduced, despite other sperm parameters being normal. Thus this method may explain a significant proportion of cases of unexplained infertility and can be beneficial in counselling involuntary childless couples need of in vitro fertilisation. 1. Introduction In western countries up to one-forth of couples in reproductive age are seeking medical help for involuntary childlessness . Despite the significant developments in the area of fertility seen during the last decades about one-third of these couples will be undiagnosed without any explanation to their problems. Although, the traditional semen parameters concentration, motility, and morphology are a golden standard in diagnosing of male infertility it has become apparent that none of these parameters recommended by the Word Health Organization (WHO)  are sufficient for the prediction of male fertility capacity. As the WHO parameters only address few aspects of sperm quality and function the discriminative power in relation to fertility is quite low [3, 4]. As a result, there has for long been searched for better markers of male fertility. During the last decades the use of assisted reproductive techniques (ARTs) has increased substantially [1, 5]. In particular intracytoplasmic sperm injection (ICSI) is used to an increasing degree. While in the beginning of the era of ICSI the indication for treatment was severe male factor infertility, now also couples with normal sperm quality request are treated with ICSI. However, IVF and ICSI are symptomatic treatments where only 25–30% of the treatments result
D. S. Guzick, J. W. Overstreet, P. Factor-Litvak et al., “Sperm morphology, motility, and concentration in fertile and infertile men,” New England Journal of Medicine, vol. 345, no. 19, pp. 1388–1393, 2001.
J. P. E. Bonde, E. Ernst, T. K. Jensen et al., “Relation between semen quality and fertility: a population-based study of 430 first-pregnancy planners,” The Lancet, vol. 352, no. 9135, pp. 1172–1177, 1998.
A. N. Andersen, V. Goossens, A. P. Ferraretti et al., “Assisted reproductive technology in Europe, 2004: results generated from European registers by ESHRE,” Human Reproduction, vol. 23, no. 4, pp. 756–771, 2008.
A. N. Andersen, L. Gianaroli, R. Felberbaum et al., “Assisted reproductive technology in Europe, 2001. Results generated from European registers by ESHRE,” Human Reproduction, vol. 20, no. 5, pp. 1158–1176, 2005.
J. Erenpreiss, M. Spano, J. Erenpreisa, M. Bungum, and A. Giwercman, “Sperm chromatin structure and male fertility: Biological and clinical aspects,” Asian Journal of Andrology, vol. 8, no. 1, pp. 11–29, 2006.
I. D. Morris, S. Ilott, L. Dixon, and D. R. Brison, “The spectrum of DNA damage in human sperm assessed by single cell gel electrophoresis (Comet assay) and its relationship to fertilization and embryo development,” Human Reproduction, vol. 17, no. 4, pp. 990–998, 2002.
W. Gorczyca, J. Gong, and Z. Darzynkiewicz, “Detection of DNA strand breaks in individual apoptotic cells by the in situ terminal deoxynucleotidyl transferase and nick translation assays,” Cancer Research, vol. 53, no. 8, pp. 1945–1951, 1993.
J. L. Fernández, L. Muriel, M. T. Rivero, V. Goyanes, R. Vazquez, and J. G. Alvarez, “The sperm chromatin dispersion test: a simple method for the determination of sperm DNA fragmentation,” Journal of Andrology, vol. 24, no. 1, pp. 59–66, 2003.
J. L. Fernández, L. Muriel, V. Goyanes et al., “Simple determination of human sperm DNA fragmentation with an improved sperm chromatin dispersion test,” Fertility and Sterility, vol. 84, no. 4, pp. 833–842, 2005.
D. P. Evenson, K. L. Larson, and L. K. Jost, “Sperm chromatin structure assay: Its clinical use for detecting sperm DNA fragmentation in male infertility and comparisons with other techniques,” Journal of Andrology, vol. 23, no. 1, pp. 25–43, 2002.
M. Spano, E. Seli, D. Bizzaro, G. C. Manicardi, and D. Sakkas, “The significance of sperm nuclear DNA strand breaks on reproductive outcome,” Current Opinion in Obstetrics and Gynecology, vol. 17, no. 3, pp. 255–260, 2005.
A. Giwercman, L. Lindstedt, M. Larsson et al., “Sperm chromatin structure assay as an independent predictor of fertility in vivo: a case-control study,” International Journal of Andrology, vol. 33, no. 1, pp. e221–e227, 2010.
D. Sakkas, G. Manicardi, P. G. Bianchi, D. Bizzaro, and U. Bianchi, “Relationship between the presence of endogenous nicks and sperm chromatin packaging in maturing and fertilizing mouse spermatozoa,” Biology of Reproduction, vol. 52, no. 5, pp. 1149–1155, 1995.
L. Marcon and G. Boissonneault, “Transient DNA strand breaks during mouse and human spermiogenesis: new insights in stage specificity and link to chromatin remodeling,” Biology of Reproduction, vol. 70, no. 4, pp. 910–918, 2004.
H. Billig, I. Furuta, C. Rivier, J. Tapanainen, M. Parvinen, and A. J. W. Hsueh, “Apoptosis in testis germ cells: developmental changes in gonadotropin dependence and localization to selective tubule stages,” Endocrinology, vol. 136, no. 1, pp. 5–12, 1995.
R. J. Aitken, M. A. Baker, and D. Sawyer, “Oxidative stress in the male germ line and its role in the aetiology of male infertility and genetic disease,” Reproductive BioMedicine Online, vol. 7, no. 1, pp. 65–70, 2003.
R. J. Aitken, D. Buckingham, K. West, F. C. Wu, K. Zikopoulos, and D. W. Richardson, “Differential contribution of leucocytes and spermatozoa to the generation of reactive oxygen species in the ejaculates of oligozoospermic patients and fertile donors,” Journal of Reproduction and Fertility, vol. 94, no. 2, pp. 451–462, 1992.
R. A. Saleh, A. Agarwal, E. Kandirali et al., “Leukocytospermia is associated with increased reactive oxygen species production by human spermatozoa,” Fertility and Sterility, vol. 78, no. 6, pp. 1215–1224, 2002.
D. P. Evenson, L. K. Jost, R. K. Baer, T. W. Turner, and S. M. Schrader, “Individuality of DNA denaturation patterns in human sperm as measured by the sperm chromatin structure assay,” Reproductive Toxicology, vol. 5, no. 2, pp. 115–125, 1991.
M. Sergerie, R. Mieusset, F. Croute, M. Daudin, and L. Bujan, “High risk of temporary alteration of semen parameters after recent acute febrile illness,” Fertility and Sterility, vol. 88, no. 4, pp. e1.970–e7.970, 2007.
R. A. Saleh, A. Agarwal, R. K. Sharma, T. M. Said, S. C. Sikka, and A. J. Thomas, “Evaluation of nuclear DNA damage in spermatozoa from infertile men with varicocele,” Fertility and Sterility, vol. 80, no. 6, pp. 1431–1436, 2003.
K. Plastira, R. Angelopoulou, D. Mantas et al., “The effects of age on the incidence of aneuploidy rates in spermatozoa of oligoasthenozoospermic patients and its relationship with ICSI outcome,” International Journal of Andrology, vol. 30, no. 2, pp. 65–72, 2007.
S. I. Moskovtsev, J. Willis, and J. B. M. Mullen, “Age-related decline in sperm deoxyribonucleic acid integrity in patients evaluated for male infertility,” Fertility and Sterility, vol. 85, no. 2, pp. 496–499, 2006.
E. W. Silver, B. Eskenazi, D. P. Evenson, G. Block, S. Young, and A. J. Wyrobek, “Effect of antioxidant intake on sperm chromatin stability in healthy nonsmoking men,” Journal of Andrology, vol. 26, no. 4, pp. 550–556, 2005.
M. Spanò, A. H. Kolstad, S. B. Larsen et al., “The applicability of the flow cytometric sperm chromatin structure assay in epidemiological studies,” Human Reproduction, vol. 13, no. 9, pp. 2495–2505, 1998.
C. G. Fraga, P. A. Motchnik, A. J. Wyrobek, D. M. Rempel, and B. N. Ames, “Smoking and low antioxidant levels increase oxidative damage to sperm DNA,” Mutation Research, vol. 351, no. 2, pp. 199–203, 1996.
J. G. Sun, A. Jurisicova, and R. F. Casper, “Detection of deoxyribonucleic acid fragmentation in human sperm: correlation with fertilization in vitro,” Biology of Reproduction, vol. 56, no. 3, pp. 602–607, 1997.
S. Sepaniak, T. Forges, H. Gerard, B. Foliguet, M. C. Bene, and P. Monnier-Barbarino, “The influence of cigarette smoking on human sperm quality and DNA fragmentation,” Toxicology, vol. 223, no. 1-2, pp. 54–60, 2006.
W. A. Robbins, M. F. Vine, K. Young Truong, and R. B. Everson, “Use of fluorescence in situ hybridization (FISH) to assess effects of smoking, caffeine, and alcohol on aneuploidy load in sperm of healthy men,” Environmental and Molecular Mutagenesis, vol. 30, no. 2, pp. 175–183, 1997.
M. Spanò, J. P. Bonde, H. I. Hj？llund, H. A. Kolstad, E. Cordelli, and G. Leter, “Sperm chromatin damage impairs human fertility. The Danish First Pregnancy Planner study team,” Fertility and Sterility, vol. 73, no. 1, pp. 43–50, 2000.
M. Spanò, E. Cordelli, G. Leter, and F. Pacchierotti, “Diepoxybutane cytotoxicity on mouse germ cells is enhanced by in vivo glutathione depletion: a flow cytometric approach,” Mutation Research, vol. 397, no. 1, pp. 37–43, 1998.
R. A. Saleh, A. Agarwal, E. A. Nada et al., “Negative effects of increased sperm DNA damage in relation to seminal oxidative stress in men with idiopathic and male factor infertility,” Fertility and Sterility, vol. 79, supplement 3, pp. 1597–1605, 2003.
G. B. Boe-Hansen, J. Fedder, A. K. Ersb？ll, and P. Christensen, “The sperm chromatin structure assay as a diagnostic tool in the human fertility clinic,” Human Reproduction, vol. 21, no. 6, pp. 1576–1582, 2006.
M. E. Hammadeh, M. Stieber, G. Haidl, and W. Schmidt, “Association between sperm cell chromatin condensation, morphology based on strict criteria, and fertilization, cleavage and pregnancy rates in an IVF program,” Andrologia, vol. 30, no. 1, pp. 29–35, 1998.
E. H？st, S. Lindenberg, and S. Smidt-Jensen, “The role of DNA strand breaks in human spermatozoa used for IVF and ICSI,” Acta Obstetricia et Gynecologica Scandinavica, vol. 79, no. 7, pp. 559–563, 2000.
A. Zini, J. M. Boman, E. Belzile, and A. Ciampi, “Sperm DNA damage is associated with an increased risk of pregnancy loss after IVF and ICSI: Systematic review and meta-analysis,” Human Reproduction, vol. 23, no. 12, pp. 2663–2668, 2008.
C.-H. Liu, H.-M. Tsao, T.-C. Cheng et al., “DNA fragmentation, mitochondrial dysfunction and chromosomal aneuploidy in the spermatozoa of oligoasthenoteratozoospermic males,” Journal of Assisted Reproduction and Genetics, vol. 21, no. 4, pp. 119–126, 2004.
E. Greco, M. Iacobelli, L. Rienzi, F. Ubaldi, S. Ferrero, and J. Tesarik, “Reduction of the incidence of sperm DNA fragmentation by oral antioxidant treatment,” Journal of Andrology, vol. 26, no. 3, pp. 349–353, 2005.
S. I. Moskovtsev, I. Lecker, J. B. M. Mullen et al., “Cause-specific treatment in patients with high sperm DNA damage resulted in significant DNA improvement,” Systems Biology in Reproductive Medicine, vol. 55, no. 2-3, pp. 109–115, 2009.