A total of 65 adult cases (53 males, 12 females) with biopsy-proven focal segmental glomerulosclerosis (FSGS) were studied. Hypertension, ascites and haematuria were seen in 13, 12 and 24 cases, respectively. Decreased creatinine clearance at presentation was found in 9 cases. Mean proteinuria per day, serum cholesterol and total protein were 7.5 +/- 4.3 g, 388.95 +/- 213.4 mg% (10.11 +/- 5.55 mmol/l) and 5.27 +/- 1.1 g% (0.527 +/- 0.11 milligram), respectively. Mesangial proliferation was seen in 13 cases and hilar sclerosis in 5. Fifty percent showed positive immunofluorescence; IgM in 10, C3 in 8, and IgG in 2. Forty-two cases could be followed (mean 32 months), out of which 38 had nephrotic syndrome and were treated with prednisolone; 58% showed response (31% complete remission and 27% partial remission). One patient in each group of responders and nonresponders had renal failure at the end of follow-up. Hypertension, degree of proteinuria, mesangial proliferation, degree of tubular atrophy and immunofluorescence findings did not significantly affect the response to steroids. We conclude that a group of patients with idiopathic adult FSGS has a favourable response to steroids, which cannot be predicted clinically.