AIDS‐related stigmatization may come from both social and illness sources. The social stigma comes from the association between HIV‐related illness and stigmatized bheaviour associated with HIV infection, notably homosexuality and IV drug use. The illness stigma comes from the disease itself ‐ the severity and contagiability of the illness. To compare social and illness stigma, 16 versions of ‘Dan’ were presented to 393 undergraduates. Four ways of transmitting HIV (homosexual behavior, IV drug use, blood transfusions, health care workers' contact with infected blood products) were crossed with four different diseases (AIDS, hepatitis, paraplegia and the flu). Dan was highly stigmatized when he was described as a homosexual or an IV drug user, as compared to a transfusion recipient or a health care worker. Also, Dan was strongly stigmatized for AIDS and hepatitis, as compared to paraplegia and the flu. There was no interaction, suggesting that these stigmas are additive, and that homosexuality and IV drug use are not the primary source of AIDS‐stigma. On the health severity index, main effects (for disease state and transmission pathway) emerged, as well as a significant interaction, suggesting that subjects were sensitive to the potential interactions among HIV‐related transmission pathways and other diseases. Copyright © 1991 John Wiley & Sons, Ltd