Developments in the treatment of stage I testicular non-seminomatous germ cell tumours have aimed primarily at reducing morbidity since the introduction of retroperitoneal lymph node dissection. Surveillance after orchidectomy, i.e. follow-up alone with chemotherapy only for relapsed disease, was found to be logistically and psychologically taxing for patients. Risk factors for relapse were, however, identified from analyses of tumour histology of the orchidectomy specimen. Between September 1988 and April 1992, 20 patients with clinical stage I testicular non-seminomatous germ cell tumours and a relatively high risk of relapse were entered into a prospective study of adjuvant chemotherapy. The chemotherapy regimen consisted of 2 cycles of cisplatin, etoposide and bleomycin. Each cycle of chemotherapy lasted 3 days. There have been no relapses at a median follow-up of 31 months (range 12-53 months). Acute and late toxicity have been modest. We have found adjuvant chemotherapy to be effective after orchidectomy in patients with stage I disease with adverse prognostic factors for relapse.