Using relational theory and survey data from the Toledo Adolescent Relationships Study (n = 665), this article examined whether individuals were tested for HIV while intimately involved in a current or recent heterosexual relationship. The analyses included the respondent's and partner's sexual risk factors (non-exclusivity and lifetime number of partners), relational variables, prior testing, and demographic characteristics. It was found that 39% of respondents had an HIV test while involved in their current or most recent sexual relationship, and women (47%), compared with men (29%), were significantly more likely to have been tested. Whereas some predictors operated similarly (number of sex partners and pressured to have sex), others displayed significant gender differences (partner's sexual exclusivity, sexual communication difficulties, and pregnancy), particularly related to women's testing behaviors. Excerpts from qualitative interviews with male respondents suggested that some relational dynamics, not well reflected in relational theory, played a role in their testing. Results highlight the need to consider gendered dynamics when targeting young adults for routine HIV testing.