Two hundred and forty-eight blood specimens collected from patients of sporadic acute viral hepatitis were serotyped with enzyme immunoassay (EIA), to study its pathogenic components during non-epidemic seasons of hepatitis A (HA). Results showed that HA accounted for 61.3% of the total sporadic acute hepatitis cases during its non-epidemic seasons, occurred mainly in youngsters and decreased with increase of their age. Hepatitis B (HB) ranked the second and accounted for 26.2%, occurred mainly in the middle-aged and the elderly and its prevalence increased with age. Hepatitis C (HC) accounted for 9.9% and hepatitis E (HE) 22.2% of the total cases, without obvious age difference. Prevalence of hepatitis D (HD) was 12.7%, with a positive rate of hepatitis D antigen (HDAg) of 12%. Superinfection accounted for 18.9%, and the viral hepatitis markers were all negative in 0.8% of the total cases. There was very significant difference in prevalence of HCV-IgG and HEV-IgG between sporadic acute hepatitis patients and blood donors during the same periods. Icterus occurred in 68% of the total cases, 86.8% in HA. Patients of HB complicated with HD were liable to chronicity.