purpose: to analyze the correlation between progins polymorphism and breast cancer. methods: a case-control study was carried out from april to october 2004. the genotypes of 50 women with breast cancer and 49 healthy women were analyzed. the 306-base pair alu insertion polymorphism in the g intron of progesterone receptor gene was detected by polymerase chain reaction and analyzed on 2% agarose gel stained with ethidium bromide. the control and experimental groups were compared regarding genotypes using the statistical epi-info 6.0 program and for frequencies the exact fisher test or c2 test were used. p value smaller p than 5% was considered to be significant. results: in relation to progins we found in the studied population a prevalence of 62 (62.6%) wild homozygous, 35 (35.3%) heterozygous individuals and two (2.1%) cases with the presence of the mutation. regarding progins polymorphism, significance was not evidenced when cases and controls were compared, as related to homozygosis (62 vs 65.3%), heterozygosis (36 vs 34,6%) or the mutation (2.0 vs 2.1%), with p=0.920 (or=1.01), 0.891 (or=1.06), and 0.988 (or=1.10), respectively. conclusions: the results show that single-gene progins polymorphism does not confer a substantial risk of breast cancer to its carriers.