Happiness is an important indicator of well-being, and little is known about how it changes in the early adult years. We examined trajectories of happiness from early adulthood to midlife in 2 Canadian longitudinal samples: high school seniors followed from ages 18-43 and university seniors followed from ages 23-37. Happiness increased into the 30s in both samples, with a slight downturn by age 43 in the high school sample. The rise in happiness after high school and university remained after controlling for important baseline covariates (gender, parents' education, grades, self-esteem), time-varying covariates known to be associated with happiness (marital status, unemployment, self-rated physical health), and number of waves of participation. The upward trend in happiness runs counter to some previous cross-sectional research claiming a high point in happiness in the late teens, decreasing into midlife. As cross-sectional designs do not assess within-person change, longitudinal studies are necessary for drawing accurate conclusions about patterns of change in happiness across the life span.