Applied a semiparametric mixture model to a sample of 284 low-income boys to model developmental trajectories of overt conduct problems from ages 2 to 8. Identified four trajectories: persistent problem, high-level desister, moderate-level desister, and persistent low. Initially high and low groups were differentiated in early childhood by high child fearlessness and elevated maternal depression. Persistent problem and high desister groups were differentiated by high fearlessness and maternal rejection. (Author/KB)