Objectives. To evaluate use of a peer-assessment tool as a performance indicator for junior pharmacists in a formal postgraduate training program in London. Methods. A 4-year retrospective analysis of data gathered using the pharmacy mini-PAT (peerassessment tool) was undertaken. Assessments, including junior pharmacist self-evaluations, were conducted every 6 months. Overall performance and performance for clustered items were analyzed to determine changes. Assessments by healthcare professionals were then compared between professional groupings, which included pharmacists, physicians, and nurses.Results. There was a significant improvement over time in both self-assessment scores and scores on assessments conducted by others using the mini-PAT. Junior pharmacists rated themselves significantly lower than did their assessors ( p,0.001); pharmacist assessors rated the performance of junior pharmacists significantly lower than did other healthcare professionals ( p,0.001). Validity, ease of use, and relevance of the pharmacy mini-PAT were demonstrated. Conclusions. As part of a range of formative evaluations involving assessors from across various health professions, the mini-PAT is a valuable instrument for developing junior pharmacists. A cohort's mini-PAT result provides a snapshot of his/her performance that can be used to identify key areas requiring further training.