Competitive polymerase chain reaction (PCR) systems were developed for rapid and quantitative estimation of HER-2 (c-erbB-2) and INT-2 oncogene amplification in paraffin-embedded ovarian cancer tissue samples. The beta-globin gene was used as reference and DNA from paraffin-embedded placenta tissue as single copy control. Reliability of the PCR method could be demonstrated by comparing dot blot data with PCR data of identical tumour samples. The PCR method was used to determine HER-2 and INT-2 copy numbers in 196 ovarian cancer samples. HER-2 and INT-2 were found to be amplified in 40 and 19%, respectively. In 8% HER-2 copy numbers were greater than five, but no high INT-2 copies were noted. Kaplan-Meier estimates did not reveal significant association with overall survival. Indirect correlation between HER-2 and INT-2 amplification was observed. The present PCR system is a valuable method for prospective and retrospective studies.