This paper examines the reporting of sexual and other risk behaviorswithin a randomized experiment using a computerized versus face-to-faceinterview mode. Biomarkers for sexually transmitted infection(STI) were used to validate self-reported behavior by interviewmode. As part of a parent study evaluating home versus clinicscreening and diagnosis for STIs, 818 women aged 18
40years were recruited in 2004 at or near a primary care clinicin São Paulo, Brazil, and were randomized to a face-to-faceinterview or audio computer-assisted self-interviewing. Ninety-sixpercent of participants were tested for chlamydia, gonorrhea,and trichomoniasis. Reporting of STI risk behavior was consistentlyhigher with the computerized mode of interview. Stronger associationsbetween risk behaviors and STI were found with the computerizedinterview after controlling for sociodemographic factors. Theseresults were obtained by using logistic regression approaches,as well as statistical methods that address potential residualconfounding and covariate endogeneity. Furthermore, STI-positiveparticipants were more likely than STI-negative participantsto underreport risk behavior in the face-to-face interview.Results strongly suggest that computerized interviewing providesmore accurate and reliable behavioral data. The analyses alsoconfirm the benefits of using data on prevalent STIs for externally
validating behavioral reporting.