Sexual discounting, which Sexual risk behaviors can arise fromdescribes delay discounting of later protected sex vs. immediate unprotected sex, or sexual discounting (e.g., sex now without a condom vs. waiting an hour to have sex with a condom), is consistently linked to sexual risk behavior. Additionally, estimates suggest that over two-thirds of HIV transmissions occur between individuals in committed relationships. Critically, current sexual discounting tasks examine sexual discounting only with hypothetical strangers, leaving a gap in our understanding of sexual discounting with committed sexual partners. We used the Sexual Discounting Task (SDT) to compare discounting rates between men who have sex with men (MSM; n = 99) and heterosexual men (n = 144), and tested a new SDT condition evaluating sexual discounting with main partners. MSM in committed relationships discounted protected sex with their main partner at higher rates than heterosexual men, and discounting rates correlated with self-report measures of condom use, impulsivity/sensation seeking, and substance use. These findings suggest that a mechanismsexual discounting is a critical factor potentially related to of increased HIV transmission between MSM in committed relationships and may be an important target for intervention and preventionand highlight a critical target for intervention.