In recent years in children and adults with acute viral hepatitis A relapses and a protracted course of the disease were described. The authors followed up 37 patients with viral hepatitis A (20 children and 17 adults) and compared the clinical course of the disease, the period of hospitalization, persistence of IgM anti-HAV antibody in serum, the incidence of relapses and protracted forms of the disease. In adults the mean hospitalization period was longer (28 days as compared with 19), the average serum bilirubin value was higher (94 mumol/l as compared with 51 mumol/l), there were more cases with obvious jaundice (59% as compared with 30%) and the early serum antibody IgM anti-HAV persisted longer (19 weeks as compared with 14 weeks). Relapses of the disease were equally frequent (12% vs. 10%), however adults had more often a protracted course of hepatitis (23.5% vs. 10%). The observed differences were not statistically significant. Almost half the cases of hepatitis affected several members of the family. The results suggest that viral hepatitis A in adult age has a more severe course than in children. The authors recommend in cases with an elevated transaminase serum activity more frequent check-up examinations to avoid missing of a relapse, and to examine repeatedly IgM anti-HAV as in protracted forms of hepatitis IgM anti-HAV may persist even when the transaminase activity is normal.