To determine the effects of planned career development activities on middle school children, 135 sixth, seventh, and eighth grade students from predominantly black middle class families were divided into two groups (experimental and control) and pre-tested using the attitude scale and competency subtests (problem solving, planning, occupational information, self appraisal, and goal selection) of the Career Maturity Inventory (CMI). For one semester the experimental group participated in a career development program. At the end of the semester students from both groups were posttested using the CMI. Additional data from aptitude and achievement tests were collected for correlational studies with the CMI competency subtests. Statistical analysis was conducted, and the following findings were reported: no significant differences were found between the groups on pretest measures, but the experimental group showed greater gains on all subtests of the CMI posttest with the exception of problem solving; the scores were significantly different on subtests of self appraisal, occupational information, and goal selection; in the experimental group there were also significant differences in the change scores between boys and girls on self appraisal and problem solving; posttest scores for each grade level were greater than the preceding grade level with the exception of problem solving in the seventh grade; all CMI subtest scores with the exception of problem solving were positively correlated with scores from aptitude and achievement tests. (BM)