This paper presents an evaluation of both process (program content) and outcome (effects on children) of a day care center and emphasizes the importance of considering process variables in order to understand program results. Subjects for the study were 25 control children who were not attending a preschool program, 25 children who attended the day care center part time, and 25 children who attended the center full time. All of the children were approximately 4 years old at the beginning of the program. The outcome evaluation focused on changes in language development, intelligence test scores, and social maturity over a 6-month period. The process evaluation involved an observational analysis and questionnaire describing teachers' behaviors in five categories: activities, materials, subjects of instruction, teacher-expressive behaviors, and program goals. The results of the outcome evaluation indicated no significant differences between the groups of any of the measures at the end of the 6-month period. The process evaluation indicated little agreement between the teachers regarding important aspects of the program. This evaluation also indicated little correspondence between teachers' ratings of the importance of various aspects of the program and their observed behaviors. The paper suggests that insignificant outcome results are more clearly understood when process variables are considered at the same time. (BD)