57 boys and 52 girls classified as insecure/avoidant or securely attached on the Strange Situation (M. D. Ainsworth and B. A. Wittig, 1969) at 18 mo were observed at home and in play groups at 18 and 30 mo. The children’s parents reported on occurrences of problem behaviors at 24, 27, 30, and 48 mo. A significant effect was found for attachment classification: Teachers and observers of the playgroups rated girls classified as insecure/avoidant as more difficult to deal with and as having more difficulty with peers than girls rated as securely attached.