AIDS-related research has documented overreactions to casual contact and underreactions to sexual risk. This contradiction is explained by "magical contagion", a principle of thinking common in traditional societies, wherein contagion is considered socially discriminating, such that harmfulness depends on the nature of the relationship between source and recipient. In Study 1, 100 undergraduate participants drew germs described as their own, a stranger's, their lover's, or a disliked peer's. Lovers' germs were depicted as less threatening than disliked peers' germs. In Study 2, scenarios described contact with a flu-infected lover, stranger, or disliked peer. New undergraduate participants (N = 133) rated how likely they were to become ill and how severely. Although likelihood ratings did not differ, severity ratings followed a linear trend, effects of lover contact being least severe and contact with disliked peer most severe. Behavioral implications of the blurring of feelings about germ source with estimates of germ virulence are discussed.