To determine whether the daily mother-infant separation involved in day care adversely affects children's emotional development, follow-up data on emotional development were compared for preschool children in day care and their home-reared counterparts. Follow-up assessments were done in the home at approximately age 3-1/2 for ten white middle class children who had been in infant day care from approximately 1 year of age and for 13 home-reared children. Measures included observations and tape recordings of mother-child interaction in structured situations, a semi-structured maternal interview which was tape recorded, and some standardized language tests. No differences were found between the two groups for the frequency and intensity of behavior problems, separation reactions, greeting responses to mothers after an hour's separation, or for anxiety manifested during testing. Significant group differences were found for compliance and temper tantrums, with day care children being less compliant with their mothers' requests to complete a boring task and exhibiting more temper tantrum behavior than the home reared children. These differences were interpreted as supporting the hypothesis that the day care children were somewhat delayed in their negotiation of autonomy from their mothers. Data on the degree to which social interactions in day care at 18 months were predictive of later emotional development are also presented. (JMB)