Understanding the transmission dynamics of HIV and other sexually transmitted infections is critically dependent on accurate behavioral data. This study investigates the effect of the mode of questionnaire delivery on the quality of sexual behavior reporting in a 2010 survey conducted in Kampala, Uganda, among 18–24-year-old women. We compare the reported prevalence of five sexual outcomes across three interview modes: traditional face-to-face interviewing (FTFI) in which question rewording was permitted, FTFI administered via computer-assisted personal interviewing (CAPI) in which questions were read as written, and audio computer-assisted self-interviewing (ACASI) in which participants listened to prerecorded questions and entered responses using a computer touchscreen. We then assess the validity of the data by evaluating the reporting of sexual experience against three biological markers. Results suggest that ACASI elicits higher reporting of some key indicators than FTFI does, but self-reports from all interview modes were subject to validity concerns when compared with biomarker data. The study highlights the important role that biomarkers can play in sexual behavior research.