Data were obtained from the Montreal Two Samples Longitudinal Study, a prospective longitudinal study of 470 males adjudicated by the Montreal Area Juvenile Court in 1974 and 1975. At recruitment, the sample consisted of 470 boys, ages 13 to 17. Structured interviews were conducted at early to mid-adolescence, mid-to late adolescence, early to mid-20's, early 30's, and early 40's. Because most of the sample had stopped offending in their 40's, the analyses focused on crime patterns up to early to mid-30's. The self-reported offenses of interest in the interviews were petty theft, shoplifting, common theft, burglary, personal larceny, motor vehicle theft, aggravated theft, vandalism, assault, disorderly conduct, drug offenses, and sex offenses. Two general crime patterns were identified as "organized" and "disorganized." The "organized" pattern was characterized by utilitarian motive, planning, and a use of instruments. The "disorganized" pattern featured offenses motivated by impulsive thrill-seeking that involved little planning and the likely use of drug and/or alcohol just prior to committing an offense. The level of organization in crime patterns, particularly in planning and the use of instruments, tended to increase with age. For those individuals who persisted in "disorganized" crime patterns from mid-adolescence into adulthood, the crimes tended to become even more disorganized and reckless. There is no clear dominant crime pattern (either organized or disorganized) in the sample with advancing age. Lack of self-control and impulsivity may be factors that determine which general pathway offenders may follow. Future research might focus on this issue. 2 tables, 1 figure, 6 notes, and 39 references