A study on nine cases of diphasic viral hepatitis A was carried out in 130 children admitted to pediatric hospital from January to December 1982. One hundred and eight children (83.0%) showed IgM anti-HAV (one of them was a chronic HBsAg carrier), 19 (14.6%) were HBsAg positive at the admission and 3 (2.3%) became positive for anti-HBc IgM marker during the course of the illness. Nine anti-HAV IgM positive children showed an atypical course of their disease in that after a short period of progressive enzyme level normalization, a relapse occurred without signs of subsequent HBV, CMV or EBV infection. Probable although hypothetical interpretations of these cases are discussed.