To assess the degree of house officers' concerns about acquiring AIDS (acquired immunodeficiency syndrome) from their patients, we surveyed 263 medical and pediatric interns and residents in four housestaff training programs affiliated with seven New York City hospitals with large AIDS patient populations; 258 questionnaires (98 per cent) were returned. Thirty-six per cent of medical and 17 per cent of pediatric house officers reported percutaneous exposures to needles contaminated with blood of AIDS patients. Forty-eight per cent of medical and 30 per cent of pediatric house officers reported a moderate to major concern about acquiring AIDS from their patients. Greater concern about personal risk was noted in those house officers who were earlier in their residency training, who reported having treated a greater number of AIDS patients, and who were in medicine rather than pediatrics programs. Twenty-five per cent of all respondents reported that they would not continue to care for AIDS patients if given a choice. The results demonstrate a substantial degree of concern about acquiring AIDS among house officers caring for AIDS patients and suggest the need for housestaff program administrators for formally address these concerns.