The present study investigates the characteristics which differentiate between first-year university students who maintain their high school averages (Maintainers: n = 165) and those whose averages decrease at least one letter grade (Decliners: n = 435). The 600 students entered first year at one of six Canadian Universities, which varied in size and ethnic diversity. Data were collected in August, prior to the start of school, and in November of first year. Multivariate analyses indicated significant group differences between Maintainers and Decliners on familial variables (gender, fathers' education level, but not family income, parental reciprocity, parental support or immigrant/generational status), psychological well-being (perceived stress in August and November, and November depression, self-esteem and health), and university adjustment (university plans, transition perception, time management and university adaptation). The current study addresses a gap in the existing academic achievement literature, while providing practical information to students, parents, and educators involved in the transition to university.