Research has consistently found that health care providers report having negative attitudes and perceptions toward Acquired Immune Deficiency Syndrome (AIDS) patients. This study was conducted to examine the independent and joint influences of a patient's mode of acquisition of illness (blood transfusion versus sexual promiscuity), patient blame (self-blame versus chance-blame), and patient sexual orientation (homosexual versus heterosexual) on medical students' attitudes toward and willingness to treat AIDS patients. Medical students in either their first year of training (N=74) or their fourth or internship year (N=44) were randomly assigned to read case vignettes which described an AIDS patient. The cases varied as a function of the crossing of the three factors under study. A consistency bias between attribution of blame and mode of disease acquisition was found to strongly influence perceptions. More positive attributions were made when such a consistency was perceived: a sexually promiscuous patient was seen as more sociable when he blamed himself for acquiring his disease than when he blamed chance and a patient who acquired AIDS via a blood transfusion was deemed more psychologically well-adjusted when he blamed chance for the acquisition of his illness rather than himself. Furthermore, the sexual orientation of the patient and general attitudes of AIDS patients influenced the providers' willingness to treat an AIDS patient. (Author/NB)