Polyarteritis nodosa (PAN), an extra-hepatic complication of hepatitis type B, is usually treated with a combination of immunosuppressive and antiviral drugs. Less commonly, interferon (IFN) has been used alone. A 57-year-old man was admitted to our hospital with epididymitis and acute hepatitis with genotype A, hepatitis B virus (HBV). He became a carrier with complicating PAN. The administration of interferon alpha2b (IFNalpha2b) at a dose of 6 MU/day for 4 weeks alleviated abdominal and neuronal symptoms related to PAN, although HBV replication was not eliminated. This is the first case of PAN with HBV of genotype A and which was treated with IFN alone. This case indicates the possibility that IFN is efficacious for extra-hepatic complications of hepatitis type B and suggests that differences in genotype may be associated with variation in the likelihood of progression to persistent infection and the incidence of extra-hepatic complications in Japan.