Thirty percent of the males and 10 percent of the females reported some involvement in aggravated assault, robbery, sexual assault, and gang fights. These rates were 35 and 11 percent, respectively, by age 21. However, the typical career in serious violent offending lasted 1 year or less. Individual serious violent offenders committed between 8 and 24 index offenses per year and between 60 and 360 total offenses in 5-9 different types of crimes each year. Some indirect evidence indicated that progressions in the seriousness and variety of offenses were occurring. Findings indicated that arrest data may overstate the magnitude of sex, race, and age differences in the serious violent offender population and that little basis exists for assuming that serious violent offenders are a unique class of offenders. Findings also suggested that prevention programs should target males ages 16-19 years. In addition, the low probabilities of arrest for a serious violent offense and the likely progressions in frequency, seriousness, and variety over the course of the career makes it seem unreasonable to make any first-offense assumption or claim that those charged and convicted of serious violent offenses. Findings suggest that the juvenile justice system should handle minor offenders routinely, perhaps through citations requiring restitution and fines, and that serious violent offenders should receive swift action and formal legal sanctions. Notes and 30 references