Six cases of hepatitis B-associated vasculitis occurred during a four-year period in Eskimos living in southwest Alaska, an area hyperendemic for hepatitis B. All showed positive results in tests for hepatitis B surface antigen (HBsAg), and all five patients tested for hepatitis B e antigen (HBeAg) showed positive values. Two patients died of the disease. Of three who recovered, two had positive values for HBsAg and HBeAg when tested two years later. In the villages of four patients, the prevalence of hepatitis B virus (HBV) infection ranged from 18.2% to 73.1%. Serological evidence of HBsAg was found in 22% and antibody to HBsAg (anti-HBs) in 30% of close relatives of the patients. Two patients had no previous serological evidence of infection with HBV, indicating that vasculitis followed recent infection. The results provide epidemiologic evidence of the clinical association between HBV infection and vasculitis.