The aim of this study was to explore the within-group effects of mother-infant attachment and day-care on children's social and emotional adaptation at 42 months and in the early school years. For this high-risk sample, the effects of day-care depended on the quality of mother-infant attachment. Day-care appeared to have a negative effect for secure children but had a positive influence for insecure children. For the secure group, children in day-care were more negative and avoidant at 42 months, and they were more externalizing and aggressive in kindergarten compared to the home-reared group. In contrast, day-care children who were insecurely attached were less withdrawn and more agentic. Overall, day-care children were rated higher on externalizing behavior in kindergarten than home-reared children, but no differences were found in the later school years. The sequelae of attachment indicated that security of attachment during infancy differentially predicted later adaptation for day-care and home-reared children. Attachment was related to later adaptation for home-reared children but did not predict later adaptation for day-care children.