Samples of human endometrial carcinomas and cervical adenocarcinomas were screened for the presence of single site DNA mutations at codon 12 of the K-ras gene using dot blot hybridization of DNA amplified by the polymerase chain reaction (PCR). Of 21 cases of endometrial carcinoma, point mutations were observed in three cases (14.3%). Mutation from GGT to GTT was seen in one case, and mutation to GAT was observed in two cases. Of seven cases of cervical adenocarcinoma, point mutations were noted in two cases (28.6%). Mutation from GGT to GTT and double mutation to GAT and GCT were in one case each. However, no correlation was found between the presence of point mutation and age, clinical stage, or depth of muscular invasion. With respect to prognosis, of five patients with point mutation, one with cervical carcinoma died, and of 23 patients without mutation, one with endometrial carcinoma died.