The findings indicate that co-offending patterns by age are not noteworthy in explaining why participation in illegal activities rises in adolescence, peak in early adulthood, and then declines thereafter. Once co-offending is differentiated from solo-offending, with solo-offending representing the bulk of criminal activity among all age groups, including juveniles, a curvilinear relationship remains between age and solo-offending and between age and co-offending. In analyzing co-offending crimes reported to police, it was found that in many types of crimes, offenders and victims came into contact, thus allowing for the estimation of the perpetrator’s age notwithstanding whether an arrest was made. The results support previous studies for the contention that co-offending among juveniles is theoretically inconsequential because youth tend to be more extroverted than adults and, as a consequence, are more apt than adults to commit crimes in groups than alone. It has been stated often that co-offending is the dominant form of criminal offending among juveniles because of the enhanced salience of peer pressure during adolescence, and that this enhanced propensity to co-offend is pivotal for understanding the age-crime curve. Using National Incident-Based Reporting System (NIBRS) data for 2002, an analysis of 466,311 criminal arrests drawn from 7 States was conducted. The purpose of the study was to investigate whether co-offending patterns influenced the curvilinear relationship between age and crime. Figures, notes and references