BACKGROUND: Despite recommendations that sexually active men who have sex with men be regularly tested for sexually transmitted infections (STIs) and that testing reflect anatomical sites of potential exposure, regular testing is not widely performed, especially for rectal STIs. As such, little is known about the prevalence of rectal and urethral STIs among young men who have sex with men (YMSM). METHODS: The current study examined the prevalence and risk factors for rectal and urethral chlamydia and gonorrhea in a sample of 1113 YMSM ages 18 to 29 years (mean, 24.07 years). Before participating in a randomized controlled trial for an online human immunodeficiency virus prevention program (Keep It Up! 2.0), participants completed self-report measures and self-collected urine and rectal samples. Participants mailed samples to a laboratory for nucleic acid amplification testing. Viability of self-collected samples was examined as a potential method to increase STI screening for MSM without access to STI testing clinics. RESULTS: Results indicated that 15.1% of participants tested positive for an STI, 13.0% for a rectal STI, 3.4% for a urethral STI, and 1.2% for both rectal and urethral STIs. Rectal chlamydia was significantly more common (8.8%) than rectal gonorrhea (5.0%). Rectal STIs were higher among black YMSM compared with white YMSM. Additionally, rectal STIs were positively associated with condomless receptive anal sex with casual partners. CONCLUSIONS: Findings call attention to the need for health care providers to test YMSM for rectal STIs. This study also demonstrates the viability of including self-collected samples for STI testing in an eHealth program.