The purpose of this study was to identify distinct trajectories of cigarette smoking from ages 14 to 32, and to examine adolescent personality factors that distinguish trajectories of smoking behavior. Participants (N = 975) were randomly selected and followed prospectively since 1975. Follow-up data on cigarette use and personality and behavioral attributes were collected at five points in time, using structured interviews given in private by trained interviewers. Of these subjects, 746 comprised the cohort used in this study. Growth mixture modeling identified five smoking trajectory groups: nonsmokers, occasional smokers, late starters, quitters, and heavy/continuous smokers. Adolescent personality and behavioral risk factors such as lower ego integration, more externalizing behavior, and lower educational aspirations distinguished the trajectory groups. No gender differences were noted. The findings supported the hypotheses indicating multiple distinct trajectory groups of smoking behavior. Smoking behavior appeared in early adolescence and most often continued into adulthood. Emotional difficulties (i.e., lower ego integration), externalizing behavior, and lower educational aspirations in early adolescence were associated both with smoking at an early age and with continuing to smoke into the thirties. To be more effective, smoking prevention programs should target personality and behavioral variations before smoking becomes habitual, particularly focused on characteristics reflecting behavioral problems as manifested in emotional difficulties, externalizing behavior, and low educational aspirations in early adolescence. The implications for research, prevention, and treatment are discussed.