A follow-up study evaluated the impact of School-Based Health Centers (SBHC) on health behaviors (including emotional and reproductive health and substance abuse), school attendance and academic performance, and health service use. The study compared these behaviors between 1990 and 1992 in several Oregon high schools with and without SBHCs. Findings indicated that health risk behaviors are already prevalent in ninth grade, implying that primary prevention needs to be initiated at a younger age. Significant gender differences were found in mental health indicators, with females reporting consistently worse emotional health. These clinics serve students with the greatest need, and those students seeking mental health or reproductive health services have worse self-esteem, higher levels of distress and more suicidal thoughts and attempts than their counterparts who seek these services at outside providers. The survey revealed high levels of satisfaction with the SBHC service, and that almost half of students have used the service. In one of the three sites studied, the SBHC was associated with global improvements in health behaviors, including decreases in substance use and sexual activity and improvements in reproductive health attitudes and behaviors. (A copy of the Adolescent Health Survey instrument and charts of the resulting statistics are appended.) (JPB)