Clinical outcome in ovarian carcinoma is predicted by progesterone receptor status, indicating an endocrine aspect to this disease. Peripheral leucocyte genomic DNAs were obtained from 41 patients with primary ovarian carcinoma and 83 controls from Ireland, as well as from 26 primary ovarian carcinoma patients and 101 controls in Germany. Southern analysis using a human progesterone receptor (hPR) cDNA probe identified a germline TaqI restriction fragment length polymorphism (RFLP) defined by two alleles: T1, represented by a 2.7 kb fragment; and T2, represented by a 1.9 kb fragment and characterised by an additional TaqI restriction site with respect to T1. An over-representation of T2 in ovarian cancer patients compared with controls in the pooled Irish/German population (P < 0.025) was observed. A difference (P < 0.02) in the distribution of the RFLP genotypes between Irish and German control populations was also observed. The allele distributions could not be shown to differ significantly from Hardy-Weinberg distribution in any subgroup. Using hPR cDNA region-specific probes, the extra TaqI restriction site was mapped to intron G of the hPR gene.