Thirty-six patients with fulminant viral hepatitis were studied. Enzyme immunoassay was used to detect the presence of HBsAg, IgM anti-HBc, and IgM anti-HAV. Non-A, non-B virus was the most common aetiological agent (61.1%) followed by hepatitis B virus (HBV; 30.6%) and hepatitis A virus (8.3%). Presence of IgM anti-HBc confirmed the diagnosis of HBV infection in three cases who were negative for HBsAg. Similarly, in one case who was positive for HBsAg, absence of IgM anti-HBc suggested superinfection with some other agent. Survival was significantly higher (P less than 0.01) in the hepatitis A virus (HAV) group (66.6%) compared with non-A, non-B (31.2%) and HBV groups (27.3%). Fever at the onset of illness was seen in all patients with HAV, 54.5% of patients with HBV and 38.88% of patients with non-A, non-B infection (P less than 0.01). The median time interval between the first symptom and the onset of encephalopathy was 16, 13 and 8 days in HAV, HBV and non-A, non-B groups, respectively, but this difference was statistically not significant (P greater than 0.05).