The prognosis of acute poststreptococcal glomerulonephritis (APSGN) is still a matter of considerable debate. In an attempt to elucidate this controversy, the medium-term prognosis was evaluated in 40 patients 5-9 years after the onset of the disease, and the long-term prognosis in 88 patients 10-17 years after the onset of the disease. All were sporadic cases. In the medium-term follow-up study, abnormalities were revealed in 5.0% (2/40) of the patients. Hypertension and proteinuria were the only abnormalities detected. In the long-term follow-up study, abnormalities were revealed in 6.8% (6/88) of the patients. Hypertension was found in 3.4, proteinuria in 2.3, and microhaematuria in 2.3% of the patients. In both studies, all patients had normal creatinine clearance. We conclude that the medium- and long-term outcome of patients with APSGN is excellent.