College students often delay or avoid seeking testing for sexually transmitted infections (STIs), even if the services are readily available. We used in-depth, semistructured interviews to survey 41 college students aged 18 to 23 years about factors that influence decisions about STI testing. We grouped statements into 9 themes that represent influences on the decision. The most frequently mentioned factors were negative consequences of testing and perceived vulnerability to infection; other issues that influenced decision making included perceived benefits, perceived severity of diseases, public knowledge and opinion, social norms, provider characteristics, test-site characteristics, and personal considerations. Social stigmas and negative consequences appear to represent significant barriers to college students' being tested, which could increase the risk of spreading infections to others. Clinicians and health educators should raise students' awareness of the need for screening and should work to reduce the barriers to screening, including social stigmas and negative consequences.