We developed a Self-Regulation Measure for Computer-based learning (SRMC) tailored toward medical students, by modifying Zimmerman's Self-Regulated Learning Interview Schedule (SRLIS) for K-12 learners. The SRMC's reliability and validity were examined in 2 studies. In Study 1, 109 first-year medical students were asked to complete the SRMC. Bivariate correlation analysis results indicated that the SRMC scores had a moderate degree of correlation with student achievement in a teacher-developed test. In Study 2, 58 third-year clerkship students completed the SRMC. Regression analysis results indicated that the frequency of medical students' usage of self-regulation strategies was associated with their general clinical knowledge measured by a nationally standardized licensing exam. These two studies provided evidence for the reliability and concurrent validity of the SRMC to assess medical students' self-regulation as aptitude. Future work should provide evidence to guide and improve instructional design as well as inform educational policy.