Between 1979 and 1996 303 men with stage I testicular germ cell tumours (120 seminoma and 183 non-seminomatous germ cell tumours (NSGCT)) were enrolled onto a programme of surveillance. In our institutions the frequency of computed tomography (CT) scans is reduced compared with other centres. For all 303 men, the median follow-up is 5.1 years (range: 0.1-21.7 years) and there have only been 3 deaths (1 from disease, 1 from neutropenic sepsis and 1 from secondary leukaemia). 52/183 (28%) patients with NSGCT and 18/120 (15%) patients with seminoma have relapsed. The relapse-free survival at 5 years is 82% for seminoma and 69% for NSGCT (Logrank P=0.004). All men who relapsed, except 1 man with NSGCT, were in the International Germ Cell Cancer Collaborative Group good or intermediate prognosis group at relapse. Half of the seminoma relapses presented with symptoms and 31% of the NSGCT relapses. The remaining relapses were detected serologically or radiologically by the surveillance programme. 5 men (2%) on surveillance, 3 with initial diagnosis of seminoma and 2 with NSGCT, have developed second contralateral testis tumours (all stage I seminomas). In a well motivated centre a policy of surveillance for stage I testicular germ cell tumours (both NSGCT and seminoma) is associated with a low mortality rate (3/303, 1%) and may have the advantage of sparing overtreatment with potentially toxic therapies in this group of young men.