Portal survey techniques involve multimodal assessments (e.g., self-report, biologic, and observational) in high-risk drinking and drug-use settings. Our investigation expanded the portal survey methodology to include follow-up assessments of emerging adult women recruited at the border as they cross to and from Mexico south of San Diego, California. The feasibility of the follow-up procedure was established, and the limitations of the technique clarified. Follow-up participants and nonparticipants did not differ by age or reported victimization. Data indicated that 8% of women experience negative events on their return to the United States after a night of binge drinking. These experiences could only be captured in a follow-up survey, as they happened after participants left the border area. (Contains 2 figures.)