We examined whether childhood factors predict age of first arrest in adolescent girls referred for placement and treatment for serious delinquency problems (N = 62). Measures included child characteristics (i.e., age of menstrual onset, childhood ADHD, and IQ), family environmental factors (i.e., severe punishment, parental transitions, and sexual abuse), biological parent criminality, and juvenile court records. Parental transitions and biological parent criminality significantly predicted the age of first arrest (M = 12.5 years), and IQ showed a trend to be a significant predictor. The final model accounted for 52% of the variance. A younger age of first arrest was related to increased health-risking sexual behaviors and to increased self-reported delinquency. Logistic regression analyses indicted that membership in an early-onset group could be reliably formed using family and child predictors, with accurate classifications for 46-90% of the girls. Family environmental and child characteristics played a strong role in predicting which girls would be arrested at an earlier age. The strong predictive utility of parental transitions and biological parent criminality, in particular, suggest two avenues for identifying girls at risk for delinquency problems.