There has been little experimental research examining characteristics that contribute to the stigmatization of individuals with sexually transmitted infections (STIs) other than HIV. We examined 3 illness characteristics (STI type, control over transmission, target gender) and 3 observer characteristics (sexual attitudes, sexual experience, observer gender) characteristics. Undergraduates (N = 207) read 1 of 8 vignettes and provided ratings of enacted stigma, felt stigma, and attributions of blame. As predicted, ratings of blame and stigmatization were significantly greater by individuals with more conservative attitudes and in the conditions in which the target had more behavioral control and contracted herpes. We found little evidence for a sexual double standard. Implications for the development and maintenance of illness-related stigmas are discussed.