This study was conducted to assess the relationship between obesity markers (Body mass index (BMI), fat percentage) and DNA oxidation marker 8-hydroxy-guanosine (OHG) , as a predictor for future clinical problems in obese adolescents of Giza. The study was conducted on 103 adolescents aged 13-18 years (22 boy, 81 girl). BMI was calculated as body weight (kg) divided by height (m2) squared and obesity was defined as BMI of 95 percentile. Fat percentage was determined by using Biological impedance technique. Oxidative stress markers as 8- hydroxyl guanosine, superoxide and glutathione were measured. The adolescents were divided according to BMI into two groups. Group I with BMI >95 percentile and less than 97 percentile (obese) and Group II with BMI >97 percentile (severely obese). Significant differences were detected between the two groups (Group I and II) of the study as regard obesity markers (BMI, fat%) and oxidative stress markers (lipid oxidation, superoxide dismutase enzyme activity, glutathione peroxidase enzyme activity, 8-hydroxyl guanosine) (p<0.0005). Significant positive correlations were detected between obesity markers and oxidative stress markers among adolescent severely obese cases (group II). Obesity is highly associated with states of oxidative stress in adolescents, with elevated levels of oxidative stress markers, with a positive relation with 8-hydroxy-guanosine and obesity markers and other oxidative markers, suggesting that this marker might play an important role in the prediction of future development of some clinical diseases.