Thirty-two cases of ovarian carcinoma, two of normal ovaries, four of benign epithelial ovarian tumor, and three of borderline epithelial ovarian tumor were studied using Southern blot hybridization of DNA. In 15 of the 32 cases of ovarian carcinoma, peripheral lymphocytes were also studied. The amplification rate of C-myc, C-N-ras, C-Ki-ras and C-erbB-2 in ovarian carcinoma were 50%, 44%, 31% and 25% respectively. The amplification of C-Ki-ras and C-N-ras took place chiefly in cases of early stage and those of good differentiation. The amplification of C-N-ras was also found in cases of advanced stage. The amplifications of C-myc and C-erbB-2 were chiefly found in cases above stage Ⅲ and those of poor differentiation. A total of 83% of the patients who died were found to have amplifications of more than 2 proto-oncogenes, with which the amplification of C-erbB-2 was involved. Thirty-two cases of ovarian carcinoma, two of normal ovaries, four of benign epithelial ovarian tumors, and three of borderline epithelial ovarian tumors were studied using Southern blot hybridization of DNA. In 15 of the 32 cases of ovarian carcinoma, peripheral lymphocytes were also The amplification rate of C-myc, CN-ras, C-Ki-ras and C-erbB-2 in ovarian carcinoma were 50%, 44%, 31% and 25% and CN-ras took place chiefly in cases of early stage and those of good differentiation. The amplification of CN-ras was also found in cases of advanced stage. The amplifications of C-myc and C-erbB-2 were chiefly found in cases above stage III and those of poor differentiation. A total of 83% of the patients who died were found to have amplifications of more than 2 proto-oncogenes, with the amplification of C-erbB-2 was involved.