This study suggested that vaccination of drug abusers with inactivated HBsAG will not prevent the development of chronic liver disease, but may slow the progression of the disease and lessen the risk of subsequent cirrhosis or hepatoma. Twenty-seven parenteral drug abusers admitted to hospital for liver biopsy between 1 January and 31 August 1981 made up the sample for this study. Twenty-two of these were male, aged between 12 and 29 years, with a mean duration of 33.6 months of intravenous drug misuse. Nearly 90% of the total sample showed evidence of non-A, non-B hepatitis. The findings suggested that a non-A, non-B vaccine will be needed.