To prospectively evaluate the effect of introducing a clinical skills "passport" on medical students' reporting of their experience with basic clinical skills. A prospective longitudinal intervention study was conducted. Medical students were administered a questionnaire at the conclusion of their 12-week surgery clerkship regarding their experience with 15 clinical skills, inquiring whether they had "learned on surgery clerkship", "learned before surgery clerkship", or "not learned". Preintervention baseline data were obtained for 2 consecutive academic years (n = 213 students). In the third year, students (n = 124) were given a clinical skills passport to document performance of 8 of the 15 skills under the supervision of a surgical resident or faculty member. After excluding from analysis those students who learned a skill before their surgery clerkship, the fraction of students who reported learning clinical skills during their surgery clerkship before and after the introduction of the clinical skills passport was compared using Fisher exact test and chi-squared test, where appropriate (p ≤ 0.003 was considered significant; Bonferroni correction for multiple comparisons). Washington University School of Medicine. A total of 337 medical students completing the junior surgery clerkship over a 3-year period were included in the study. All 337 students completed a survey. Considering each skill individually, survey response rate was 5045/5055 (99.8%). Combining all responses for all skills, the fraction of students reporting that skills were learned on the surgery clerkship increased after the introduction of the clinical skills passport (1498/1938 [77%] preintervention vs. 974/1109 [88%] postintervention, p < 0.0001, chi square). After the introduction of the clinical skills passport, the fraction of students reporting that a skill was "learned on surgery clerkship" significantly increased for the 8 skills listed on the passport (1026/1699 [83%] preintervention vs. 685/714 [96%] postintervention, p < 0.0001, chi square), but did not increase for the 7 skills not listed on the passport (472/695 [68%] preintervention vs. 289/395 [73%] postintervention, p = 0.08, chi square). Considering each skill individually, after the introduction of the clinical skills passport, the fraction of students reporting that a skill was "learned on surgery clerkship" significantly increased for 4/15 skills (all listed on the clinical passport) and decreased for 0/15 skills (p < 0.003, Fisher exact test, 2 tailed). Institution of a clinical skills passport system during a surgery clerkship increased medical student reporting of their performance of basic clinical skills.