Background: DNA sequence variations in HIF-1α gene might yield changes both in the production outcomes and in the activities of the gene. Overexpression of the HIF-1α subunit, resulting from intratumoral hypoxia and genetic alterations, has been demonstrated in common human cancers and is correlated with tumor angiogenesis and patient mortality. In this study, we aimed to determine how the three single nucleotide polymorphisms (SNPs, C1772T and G1790A exon 12, C111A exon 2) in the HIF-1α gene coding regions affect the ovarian, cervical and endometrial cancer patients in the Turkish population. A study on this relationship has not been conducted to date. Method: 102 gynecologic cancer patients and 107 healthy controls were studied. Genotypes of the three polymorphisms were analyzed by PCR-RFLP. Results: There was no significant difference between ovarian cancer patients and controls in terms of the distribution of C1772T genotypes and alleles (P > 0.05). However, there was a highly significant increase in the frequency of both CT 1772 and TT 1772 genotypes in patients with cervical and endometrial cancers compared with healthy controls. In fact, 1772T allele-carriers (CT + TT genotypes) showed an association with the risk of cervical and endometrial cancers compared to the wild type (OR = 3.84, 95% CI: 1.65-8.93; OR = 7.41, 95% CI: 2.33-23.59, respectively). C1772T polymorphism was not associated with family history concerning gynecologic and/or other cancer types, stages (I-IV) and grades of tumor, smoking habits and existence of other diseases that generate a hypoxic microenvironment even after multivariable logistic regression analysis. As for HIF-1α G1790A genotypes, the frequencies of G alleles were 98% in ovarian patients and 100% in the control group. We found no significant difference in the genotype distribution and allele frequencies between the ovarian patients and healthy control subjects. There were no GA and AA genotypes among the cervical and endometrial cancer patients. As for HIF-1α C111A polymorphism, we did not find CA and AA variants of the gene in controls or in any of the three types of patients. Conclusion: Our results suggest that the C1772T polymorphism of the HIF-1α may be associated with cervical and endometrial cancers. © 2007 International Society for Preventive Oncology.