The first three police contacts were examined because they included the earliest point at which a youth could be prosecuted by Philadelphia's Habitual Offender Unit (HOU). Study data were obtained from a cohort of black and white males born in 1958 who resided in Philadelphia while they were between 10 and 18 years of age. Statistical analysis was based on information obtained from police and court records. Independent variables were designed to identify future serious habitual offenders, and dependent variables represented specific aspects of a juvenile's future criminal career. Dependent variables were computed in various ways to reflect different criminal career aspects: rate per year of police contacts, average seriousness per police contact, average seriousness per year of police contact, average number of criminal charges per police contact, and average number of criminal charges per year. Dependent variables were calculated for four crime types, in increasing order of restrictiveness: all offenses, specified felonies, Uniform Crime Reports (UCR) index crimes, and UCR violent index crimes. Study findings failed to produce a tool that enhanced decisionmaking about which juveniles to direct to priority prosecution because of their expected high rates of serious offending. Despite sparse study findings, it was determined that prior police contact and offender age were related to serious habitual offending. Future research is recommended to explore whether current HOU selection criteria can be redefined, whether early warning signals of future criminal careers can be detected, and grounds for bridging juvenile and adult prosecution. Recommendations are offered to advance the detection of early warning signals of serious habitual offending.