Twenty-one patients with Stage IIA or B seminoma have been treated post orchidectomy by a single course of carboplatin prior to conventional radiotherapy in either the Royal Marsden Hospital or the Norwegian Radium Hospital during 1989-1993. Follow-up ranged from 8 months to 51 months with a mean of 36 months and median 34 months. All patients achieved complete remission and remain disease free. The main side-effects were nausea and vomiting while haematological toxicity was slight. There was no symptomatic peripheral neuropathy, ototoxicity or deterioration of renal function. This combined modality approach is rational, feasible, and effective, although a larger number of patients with longer term follow-up are needed for reasonable comparison with the use of infradiaphragmatic radiotherapy alone.