70 cases of focal glomerulosclerosis (FGS) followed for periods ranging from 1 to 24 years are reported. 39 patients had a nephrotic syndrome. 31 patients had asymptomatic proteinuria. 97 renal biopsies were performed. At least one biopsy specimen from every patient showed focal and segmental involvement of glomeruli, but no lesions were observed on the first biopsy in 6 patients. 26 of the 35 patients with a nephrotic syndrome were treated with steroids alone and/or chemotherapy and/or indomethacin. Resistance to treatment was encountered in 21 patients. Complete remission was observed in 6 cases, despite persistence or accentuation of histological lesions on serial biopsies in 3 cases. Actuarial renal survival rate at 10 years was 45% in the group with a nephrotic syndrome versus 91% in patients with proteinuria. FGS with a persistent nephrotic syndrome represents the 'malignant' form of the disease. Recurrence of the disease was observed after transplantation in 2 cases and was absent in 1.