This study of 62 low-income families examined the relation between maternal and infant measures assessed at 18 months infant age and child behavior problems at age 5 as rated by preschool teachers. The infancy assessments included measures of mother-infant interaction, maternal psychosocial problems, infant cognitive development, and infant attachment security, including the disorganized/disoriented classification. The strongest single predictor of deviant levels of hostile behavior toward peers in the classroom was earlier disorganized/disoriented attachment status, with 71% of hostile preschoolers classified as disorganized in their attachment relationships in infancy. Maternal psychosocial problems independently predicted hostile aggression in preschool and combined additively with infant attachment security in prediction. Results are discussed in relation to the asymmetry of forward and backward prediction that characterized the findings and in relation to the potential significance of disorganized attachment behavior as a precursor to later maladaptation.