Does audio computer-assisted self-interviewing (ACASI) produce more valid reporting of sexual activity and related behaviors than face-to-face interviews or self-administered interviews? This analysis, based on data collected from over 6,000 unmarried adolescents in two districts of Kenya-Nyeri and Kisumu-indicates substantial and significant differences in reported rates of premarital sex across interview modes, although not always in the expected direction. Our assumption that girls underreport sexual activity in face-to-face interviews by comparison with ACASI is not confirmed by the Nyeri data, but our results from Kisumu are considerably more promising. As for boys, who we believe exaggerate their level of sexual activity in face-to-face interviews, a more nuanced set of expectations regarding the reporting of sensitive behaviors was offered; our results from Kisumu, although not always significant, by and large conform to expectations.