Nineteen paraffin-embedded breast cancer tissue samples selected for long survival (more than 5 years) were analysed for detecting the amplification of the c-erbB-2 (Her-2/neu) oncogene by Polymerase Chain Reaction (PCR). Strong correlation was elucidated between c-erbB-2 amplification and survival; such correlation was also observed with histopathologic types and nuclear grading. Because of the similarity of the breast and ovarian cancer in the etiology of the diseases, amplification of c-erbB-2, c-myc and Ki-ras genes was examined in 32 ovarian carcinoma samples (stage I-IV). In ovarian carcinomas c-erbB-2 amplification occurred in 34% (11/32) of the fresh tumour samples, and correlation between amplification and clinical staging at P < 0.05 significance level was observed. Amplification of c-myc was detected in 9% (3/32) and none of the tumours showed amplification of Ki-ras.