Evaluation results are reported for the Southwest Educational Development Laboratory's Thinking and Reasoning Program, designed to develop analytic thinking and problem-solving skills in young children in multicultural classroom settings. Results are based on a pilot test of the program conducted during the 1974-75 school year. Mastery activities, constructed to serve as transfer tasks for several lesson sequences, were administered on a pre/post sequence basis to six kindergarten and three first-grade project classrooms and to three kindergarten and two first-grade comparison classrooms. Classrooms were ethnically mixed. Analyses of covariance demonstrated that both the kindergarten and first-grade project groups significantly outperformed their respective comparison groups in the analytic thinking areas of observing, causal reasoning, and flexibility. (Author/BF)