Effects of medical, family, and scholastic conditions were evaluated for the number and type of offenses and test score performances in 1,962 urban delinquents. Conditions were evaluated using multivariate followed by univariate analysis of variance with post-hoc tests. There were subgroup differences in the number and type of offenses and test score performances. Also, interactions of medical, family, and scholastic conditions changed the number and type of offenses and lowered test scores. Findings supported a developmental biopsychosocial model of delinquency that emphasized the predominance of medical/scholastic conditions. Orphaned or one-parent delinquents with nervous system or neonatal conditions, retardation, or hyperactivity committed assault.