The aim of this study was to evaluate the risk of subsequent non-germ cell cancer (SNGC) among men with germ cell cancer and the significance of radiotherapy and chemotherapy as risk factors. The study group consisted of 2006 male patients treated for germ cell cancer at the Norwegian Radium Hospital from 1952 to 1990 with a mean follow-up of 12.5 years. A group of 1194 patients had received radiotherapy only, 346 patients chemotherapy only (mainly cisplatin-based), 277 patients both radiotherapy and chemotherapy (mainly cyclophosphaoffe and doxorubicin-based), and 189 patients no cytotoxic treatment. A total number of 153 SNGCs were diagnosed after a mean interval of 15.9 years. The RR was 1.65 (95% confidence interval (CI), 1.4-1.9), and the mean cumulative risk after 15 years 7.8% (95% CI, 6.2-9.5%). Significantly elevated RRs were found for gastrointestinal cancer combined, cancer of stomach, liver and biliary system, lung, melanoma, bladder and sarcoma. Significantly elevated RRs were found in patients who had received radiotherapy (with or without chemotherapy), and the trend increased with very long follow-up. Patients given both radiotherapy and chemotherapy experienced the highest risk (RR = 3.54; 95% CI, 2.0-5.8), probably due to a high cumulative dose of cytotoxic treatment. Modern chemotherapy did not seem to increase the risk of SNGC, although this study's size and follow-up period did not allow definite conclusions as regards this risk factor.