The mediational linkage between class inclusion and role-taking skills was investigated by studying the effects of a successive perspective-taking training technique on the consolidation of class inclusion structures. Sixty preoperational Irish boys were given two pretest measures of class inclusion and two of role-taking. They were then grouped into one of 3 conditions: role-taking training, class inclusion training, or the control group. Subjects in the role-taking training group were given Flavell's cartoon role-taking task (Flavell et al., 1968, task 1D). At each of three points in the cartoon story the subjects were asked to imagine three possible outcomes. Subjects in the control group were read a story. The mean posttest scores of the training groups were significantly superior to those of the control group for both role-taking and class inclusion. The fact that subjects trained in perspective taking improved in class inclusion lends support to the Piagetian notion of structures d'ensemble. (Author/SS)