Little is known about the course and outcomes of adolescent gambling. This prospective study describes findings from a 3-wave (Time 1 [T1], Time 2 [T2], and Time 3 [T3]) assessment of gambling behaviors among youth (N = 305). Stable rates of any gambling and regular gambling (weekly or daily) were observed across T1, T2, and T3. The rate of at-risk gambling significantly increased at T3 (young adulthood), whereas the rate of problem gambling remained stable over time. Several adolescent risk factors were associated with either T3 at-risk or problem gambling, many of which are risk factors for adolescent substance abuse. Findings suggest that important to the origins of young adult gambling problems are risk factors associated with the problem behavior syndrome of adolescence.