We tested the feasibility and performance of the Interactive Voice Response Technology (IVR) in the assessment of sexual behavior self-reports, relative to self-administered questionnaire (SAQ) and Timeline Followback (TLFB) methods. The sample consisted of 44 sexually active Hispanic students recruited at the University of Texas at El Paso who reported daily about sexual behaviors and substance use. Thirty-three participants (75%, 18 women, 15 men) were retained for at least 80 days of the 91-day IVR. At follow-up, sexual behaviors and substance use were assessed by questionnaire (summary) reports and by TLFB, referring to the same 3-month interval. ANOVAs with normalized variables indicated less reporting in the TLFB and over-reporting of substance use in the questionnaire relative to the daily IVR self-reports. Gender moderated the effects of assessment mode, which were observed among women only. HLM analyses indicated a significant decrease in self-reports over time, suggesting reactivity of self-monitoring via IVR on behavior.