This letter to the editor concerned the incidence of delta antigen in the serum of patients with hepatitis B. The authors stated that this was common for drug abusers with simultaneously-acquired hepatitis B and delta infection. The authors based their statement on evidence from a study of 217 HBsAg-positive drug abusers during an outbreak of hepatitis B in Dublin, which began in 1981. They stated that most delta infections in Dublin were among drug users, who contracted hepatitis B and delta infection simultaneously, and who had not been proven to be more severely ill than those with acute hepatitis B only.