HIV testing was assessed online among men accessing a sexual networking website for men who have sex with men. Most of the 8,040 participants reported HIV testing (58.2% ≤ 1 year; 33.1% > 1 year) and 17.1% were HIV-positive. Overall, 8.6% of men including 24% of those 18-24 years of age had never been tested. Among never testers, 25% did not know where to get tested. Predictors of never being tested included younger age (18-24), bisexual or heterosexual orientation, living outside of large metropolitan areas, and not having a healthcare provider. Increasing access to and knowledge of HIV testing sites is needed.