Three variables were experimentally manipulated by simulation measurement using six vignettes in a completely randomized, partial hierarchical, experimental design: medical diagnosis (AIDS v. non-AIDS), sexual orientation (heterosexual v. homosexual) and intravenous drug-use history (IVDU v. non-IVDU). Following each vignette, the same Prejudicial Evaluation Scale (PES) and Social Interaction Scale (SIS) were used to measure nurses' attitudes toward patients and their willingness to interact with patients. Vignette questionnaires were randomly assigned to 360 acute-care nurses. Although sexual orientation was found not to influence PES and SIS scores, an AIDS medical diagnosis and a history of intravenous drug use were found to increase nurses' negative attitudes toward patients significantly and reduce their willingness to interact with patients. Study findings did not vary according to nurses' age, academic preparation or previous practice experience with patients with AIDS.