There is a concern over long-term retention of knowledge in professional programs. The goal of this study was to evaluate the retention of veterinary clinical pathology knowledge between the fourth-semester and fourth-year clinical pathology courses. We hypothesize that students will forget a significant amount of content area knowledge between the fourth semester and fourth year in the Doctor of Veterinary Medicine (DVM) program. We further hypothesize that a review of material during the fourth-year clinical pathology rotation will help students rebuild existing knowledge and increase performance on specific test questions, between T2 (rotation pre-test) and T3 (rotation post-test). Initial mastery of course material was assessed via a 94-item multiple-choice final exam (T1) given in the semester 4 clinical pathology course. Retention of course material from semester 4 to year 4 was assessed via a 55-item multiple-choice pre-test, administered at the start of the clinical pathology rotation in year 4 while learning/mastery during the clinical rotation was assessed via a 55-item multiple-choice post-test, administered at the end of each clinical pathology rotation. In this study, evidence of knowledge retention between semester 4 and year 4 was 55.5%. There is a small increase in the measure of knowledge gain from the beginning to the end of the rotation. As an added benefit, we were able to use identified trends for retention of knowledge within specific subject areas as a mechanism to evaluate the effectiveness of our course and reallocate additional instructional time to topics with poorer retention.