We evaluated, with a questionnaire, ethical attitudes towards the clinical attention of patients with AIDS in 88 physicians. Most of the surveyed were residents and all were working in two mexican hospitals with experience managing patients with AIDS: The National Institute of Nutrition and the National Institute of Respiratory Diseases. None of the questions was answered similarly by all physicians and some of them considered ethically unquestionable, behaviours that traditionally are immoral or even illegal. Reproducibility of the results, evaluated in 10 doctors 5 months later, was acceptable. Ethical attitudes were heterogeneous and inconsistent in the surveyed. This can be the results of a poor or absent training in Medical Ethics in medical schools and during residencies. We believe this deficiency helps maintaining discriminatory attitudes against patients with AIDS and may decrease the quality of medical services to the group.