Sixteen seventh and eighth graders previously identified as having behavioral problems earned significantly higher post-test scores on a test of REBT concepts immediately after participation in a Rational Emotive Behavioral Therapy (REBT) training program, and this knowledge was retained after an 8-week follow-up period (p less than 0.01). Additionally, the 7th graders' post-test scores were significantly higher than the pre-test scores of the 8th graders (who served as a waiting control group). Although the number of office referrals did not decrease sufficiently to produce a statistically significant reduction from baseline to intervention or from baseline to follow-up, moderate to large effect sizes were found. Participants' level of rational thinking and (stated) action were evaluated through written responses to anger-inducing scenarios; rationality of stated actions increased and rationality of thinking increased for the 7th graders and decreased for the 8th graders. Children were successful in acquiring REBT-based principles, and to some extent, in applying these to reduce aggressive behavior. Recommendations for school psychologists in using a rational emotive behavioral approach with middle school students are provided.