We have identified hepatitis D as an etiologic cause of an outbreak of 'hepatitis' in an endemic area for hepatitis B in South Kashmir, India. Thirty-five of the 51 patients with jaundice were hepatitis B virus carriers. Twenty-two of the 24 such patients tested had hepatitis D (hepatitis D virus superinfection). Two of the 3 patients with acute hepatitis B were coinfected with hepatitis D virus (HDV). Thirty-six asymptomatic household contacts of hepatitis D patients were assessed. Six were hepatitis B virus carriers, 3 of whom had HDV superinfection. Two contacts had acute hepatitis B, one with HDV coinfection. The disease occurred in adults with a mean age of 28.2 +/- 10.5 years (range 10-56 years) and was equally distributed between the sexes. Three patients with HDV superinfection presented with fulminant hepatic failure with a fatal outcome. All the patients with non-fulminant hepatitis D showed apparent clinical recovery. However, in the subsequent follow-up at 4 years, 7 patients with HDV superinfection had evidence of chronic hepatitis. One of these 7 patients died due to progressive chronic liver disease.