Smoking initiation typically occurs in adolescence and increases over time into emerging adulthood. Thus adolescence and emerging adulthood compose a critical time period for prevention and intervention efforts. To inform these efforts, this study used latent growth mixture modeling to identify 6 smoking trajectories from ages 13 to 23 among 5,914 individuals: nonsmokers (28%), stable highs (6%), early increasers (10%), late increasers (10%), decreasers (6%), and triers (40%). By age 23, the trajectories merged into 2 distinct groups of low- and high-frequency and their standing on age 23 outcomes reflected this grouping. Consideration of these results can help researchers identify at-risk individuals before their smoking becomes too problematic, providing an opportunity for intervention and possible prevention of nicotine dependence.