The relationship of background factors to separation reaction and social emotional adjustment at the start of nursery school was examined in 106 middle-class 4-year-olds. Mothers completed the Cain-Levine Social Competency Scale and questionnaires on the social experience of their children. Ratings of reactions to separation and of adjustment were obtained on the first day of nursery school and one and five weeks later. Experience with playmates at home, experience in group settings away from home, and contact with different baby sitters in the home were each independently related to ease of initial separation. A total social experience score correlated -.46 (p<.001) with separation distress. The social experience score was not related to fifth-week separation problems but was correlated with adjustment through the fifth week. Social competency was not related to separation reaction ratings or social experience but was correlated with adjustment through the fifth week. The results supported the view that the distress which some children exhibit at the start of nursery school is a function of the novelty of the situation for the child in question. [Filmed from best available copy.] (Author)