Introduction: Many medical schools in the United States are introducing leader and leadership curricula. However, there is a large gap regarding how to assess leader performance during undergraduate medical education.With the guidance of a conceptual framework, leadership assessment measures can be developed, learners can makeexpected improvements in performance over time, and assessment measures can be used in relevant, applied, medicalteaching settings. Uniformed Services University (USU) medical students are educated to become healthcare leaderswho can perform effectively in various settings. Medical students are assessed on multiple occasions for elements ofleader performance during "Operation Bushmaster"-the capstone military medical field practicum event for fourthyear medical students-by experienced faculty. A conceptual framework guides the assessment approach for leaderperformance during Bushmaster. The USU Leader and Leadership Education and Development program developed anassessment tool to measure student leader performance used in a military medical field practicum. The present paperexamines whether: (1) leader performance can be measured at Bushmaster; (2) leader performance changed duringBushmaster; (3) leader performance elements are related to each other; and (4) overall leader performance is related toother medical academic performance. Materials and Methods: Trained faculty assessed students' leader performance.Data from three cohorts of USU medical students (N = 509) were collected. All data were collected, compiled, deidentified, and analyzed with approval from the USU Institutional Review Board (Protocol number: KM83XV).Descriptive statistics, repeated measures t-tests, trend analyses, and correlation analyses were performed. Results: Datawere available from 483/509 [95%] students. Results revealed that: (1) average leader performance was satisfactory;(2) overall leader performance and performance on each of the major elements of leader performance significantlyimproved over the course of Bushmaster; (3) major elements of leader performance were significantly correlated witheach other and with overall leader performance; (4) leader performance was not correlated with students' performanceon the MCAT total score or USMLE Step exam scores. Conclusion: With the guidance of a conceptual framework, theassessment tool was used to assess leader performance in a relevant, applied, medical teaching setting. The findings ofthis study indicate that leader performance can be measured. Additionally, leader performance appears to be a separateskillset from medical academic performance and both types of performance can be taught and developed. This was aretrospective correlation study and was conducted during a military medical field practicum at a single institution.Gathering additional validity evidence of the assessment tool is needed. With additional validity evidence, the assessment tool could be applied to other medical exercises in different settings and help with the assessment of leader performance beyond medical school.