Accurate reports are important in health research, yet abortions are underreported in surveys by almost half. This study examined influences on reporting of abortion among adolescents. Participants were 63 young women from varied ethnic backgrounds who had undergone abortions at urban abortion clinics. Participants reported on their willingness to be honest about their abortion in various research settings and in comparison with other sensitive topics. Willingness to report was also examined in relation to the sponsor of the research, the mode of administration, and the characteristics of the interviewer. Adolescents indicated less willingness to report abortion than some behaviors such as cigarette smoking, but they were more willing to report abortion than family income, oral sex, or anal sex. Comparison of willingness to report across research settings indicated that face-to-face interviews appear to generate more accurate reporting than telephone surveys. The implications of these findings for the study of other health behaviors are discussed.