Relations between attachment and child emotional and behavioral regulation were studied longitudinally in a sample of 223 children from urban, low-income families. Attachment in the Strange Situation at 12 and 18 months was scored using the infant classification system and at 24 months was scored using a preschool classification system. Only modest stability was found in attachment whether within or across classification systems, with the percentage of insecure attachments consistently increasing over time. Results indicated both concurrent and predictive associations with indices of child regulation based on observer ratings or maternal report. However, only the 24-month classification predicted maternal report of externalizing and internalizing behavior problems at age 3.5 years, with additional variance accounted for by selected measures of child emotional and behavior regulation from the same assessment. Attachment security (B) and atypical attachment classifications (D, A/C, and AD) appear to provide the most consistently useful information about child functioning. Results are discussed in terms of continuity and change from the perspective of developmental psychopathology.