Forty-six patients with early (Stage I and II) ovarian cancer referred as free of residual disease after primary surgery, selected for high-risk features, were treated with adjuvant single-agent alkylating therapy comprising either intravenous cyclophosphamide (1 g/m2) in 36 patients, or oral melphalan (0.2 mg/kg daily for 5 days) in eight. Cyclophosphamide was repeated every 3 weeks for 10 cycles and melphalan every 6 weeks for 12 cycles. With a median follow-up of 36+ months, 18 patients have relapsed. The actuarial 5-year relapse-free survival was 48% and the overall 5-year survival was 54%; median survival was 84 months. Pretreatment FIGO stage was the single most important predictor of relapse-free and overall survival duration. For patients with Stage IA and IB tumours the 5-year actuarial relapse-free survival was 89%; for patients with stage IC and II (all substages), the 5-year relapse-free survival was 24% (P = 0.001). For this latter group adjuvant single alkylating agent therapy was not adequate and alternative therapeutic regimens are required. The problem of suboptimal primary surgical staging is also addressed.