Using longitudinal data from the UCLA Cooperative Institutional Research Program (CIRP) and Your First College Year (YFCY) surveys, this study examines predictors of the likelihood that science-oriented students would participate in a health science undergraduate research program during the first year of college. The key predictors of participation in health science research programs are students' reliance on peer networks and whether campuses provide structured opportunities for first-year students even though only 12% of freshmen in the sample engaged in this activity. These experiences are particularly important for Black students. The findings inform efforts to orient students at an early stage, particularly under-represented minorities, toward biomedical and behavioral science research careers.