This paper provides a review of studies published between 1998 and 2006 that have evaluated the relationship between non-maternal childcare and children's social-behavioral adjustment. Recent studies have focused on how the factors of non-maternal childcare quantity, quality, type and timing interact with factors of family background and child characteristics to affect various indicators of social-behavioral adjustment. Findings indicate that average weekly hours of non-maternal childcare is the strongest and most consistent childcare predictor of social-behavioral outcomes. Entry into childcare during the first year and extensive non-maternal childcare throughout early childhood predicts less social competence and cooperation, more problem behaviors, negative mood, aggression and conflict. When family background factors are also considered, maternal sensitivity is the most consistent predictor of social-behavioral adjustment. New theoretical frameworks and methodologies are needed to explore the mechanisms through which early, extensive non-maternal childcare negatively affects social outcomes.