AIMS: To estimate trajectories of gambling variety from mid-adolescence to age 30 years, and compare the different trajectory groups with regard to the type and the frequency of gambling activities practiced and gambling-related problems. DESIGN: Prospective longitudinal cohort study. SETTING: Province of Quebec, Canada. PARTICIPANTS: A mixed-gender general population cohort assessed at ages 15 (n = 1882), 22 (n = 1785) and 30 (n = 1358). MEASUREMENTS: Adolescent and adult versions of the South Oaks Gambling Screen (SOGS). FINDINGS: Group-based trajectory analysis identified three distinct trajectories: a late-onset low trajectory (26.7% of sample) initiating gambling at age 22, an early-onset low trajectory (64.8% of sample), characterized by one to two different activities from age 15 onwards and a high trajectory (8.4% of sample), with an average of four to five different activities from age 15 to 30. Males (14.2%) were four times more likely to be on a high trajectory than females (3.5%) (P < 0.001). Preferred types of gambling activities were similar across the three trajectories. Participants on a high trajectory reported higher gambling frequency at ages 15 and 30, and were more likely to experience problem gambling at age 30: 3.09 [95% confidence interval (CI) = 1.66, 5.75] and 2.26 (95% CI = 1.27, 4.04) times more, respectively, than late-onset low and early-onset low participants, even when socio-economic status (SES), frequency of gambling and problem gambling in adolescence, gender, age 30 education, SES and frequency of gambling were controlled. CONCLUSIONS: Engaging in several different types of gambling in early adulthood appears to be a risk factor for emergence of problem gambling.