This study investigated the emotional effects of various treatment conditions on children starting nursery school. Subjects were 108 children, predominantly middle class, 3 1/2 to 5 years old. Treatment conditions were analyzed according to (1) previsit to school vs. no previsit, (2) mother present vs. mother absent, (3) peer group experiences vs. no experience, and (4) male vs. female. Children's emotional reactions were rated according to (1) reaction to separation from mother, (2) position and activity relative to others in the last 20 minutes of each session, (3) motility (locomotion in the environment), (4) feeling toward school, and (5) comfort in class. All emotional reactions, except motility, were mutually intercorrelated. The teachers' rating of comfort had the highest correlation with the other indices of emotional reaction. The four experimental treatment variables had no significant effect on a child by the last 20 minutes of the first session, and follow-up studies supported this finding. It is concluded that most middle class children readily adapt to a nursery school situation, regardless of treatment conditions at time of entrance. (DR)