A series of 89 adult-onset nephrotic patients with minimal changes on renal biopsy was analyzed to compare the rate of response to corticosteroids and cytotoxic agents and the stability of remission or frequency of relapses at different ages. Severe hypertension and diminished renal function were more common in patients aged over 60 years, who formed 22.5% of the group. Seventy-five patients were given a first course of prednisolone in an initial dose of 60 mg/24 hr. After an eight week course of tapering doses of corticosteroids, only 45 of the 75 patients were in complete remission, 55 patients after 16 weeks and eventually 58 lost their proteinuria. The respective estimates of remission were 60%, 76% and 81%. Subsequently, of the 58 treated patients who responded, 24% never relapsed. Fifty-six percent of the patients relapsed on a single occasion or infrequently, and only 21% were frequent relapsers. Cyclophosphamide was used in 36 patients, in two as initial treatment, in 11 because of corticosteroid resistance, and in the remainder because of relapses. The time-course of loss of proteinuria was similar to that following treatment with corticosteroids, 25 (69%) losing proteinuria within 16 weeks. Only four patients failed to lose their nephrotic syndrome. Two of them had presented in acute renal failure and all four were over 60 years of age. The stability of remission after cyclophosphamide was better than that reported for children, only 13 of 36 showing relapses and 66% being in remission at five years, after which no further relapses were seen.(ABSTRACT TRUNCATED AT 250 WORDS)