The ongoing HIV epidemic among men who have sex with men (MSM) in New York City and the increased use of Internet sexual social networking websites by MSM fosters a need to understand the characteristics and sex-related behaviors of this group. The authors conducted an online survey of 195 MSM who use sexual social networking websites in New York City. Demographic characteristics, sexual sensation seeking, and HIV optimism-skepticism were compared among participants reporting sex with and without condom use (safe sex and high-risk sex, respectively) with partners met online. There was no difference in income, education, race, or employment status between the groups. The groups differed significantly in age, sexual sensation seeking, and HIV optimism-skepticism. In a multivariate logistic regression both HIV optimism-skepticism (p < .05) and sexual sensation seeking (p < .05) were significant predictors of high-risk sexual behavior (pseudo-R(2) = .24). This information should be considered when developing interventions for this group. For example, to reach those with high sexual sensation seeking, public health professionals should design sex-positive prevention messages for online distribution that highlight safer sex without condemning risky sexual practices.