The results indicate (1) higher rates of substance use at the beginning or end of the academic year for a substantial subset of the sample and (2) significant predictive relationships between day-to-day substance use observations with some weekly patterning of behavior. The study provides unique insights into the patterns and predictive relationships within tobacco smoking, alcohol, and marijuana use during the critical transition to college and across the first academic year. However, future research is needed to establish the generalizability of substance use patterns described in this study. This study employs a longitudinal design with weekly follow-back records of daily substance use across the first-year of college and addresses the following questions: (1) what individual patterns of tobacco smoking, alcohol, and marijuana use exist among first-year college students and which are most prominent and (2) what predictive patterns are present within individual substance use behaviors? Univariate time series analysis was employed to evaluate behavioral trends for each substance across the academic year. Figures, glossary and references