To assess the knowledge of hospital doctors about patients at increased risk of infection with human immunodeficiency virus (HIV) or hepatitis B virus, and the precautions they took during phlebotomy in such patients, an anonymous postal questionnaire was sent to all 307 hospital doctors working at two District General Hospitals in Liverpool, UK. Two hundred and thirty-eight (77·5%) of the questionnaires were returned. More than 90% of respondents considered a history of male homosexuality, intravenous drug abuse, prostitution or a child of a prostitute to indicate an inoculation risk. There was uncertainty about a previous prison sentence in the 1980s, residence in a home for the mentally handicapped, previous residence in the tropics and hospital treatment in the tropics. Thirty-eight percent of doctors would never enquire about sexual preference, 54·1 % about a previous prison sentence and 15·7% about intravenous drug abuse in their clinical history. Although 97·4% of doctors would sometimes or always wear gloves during phlebotomy of an inoculation risk patient, 25·5% always resheathed the needle after phlebotomy and 20·8% would never take the sharps box to the patient. More effort is required to identify accurately inoculation risk patients and greater care is needed in phlebotomy techniques. © 1991.