Those in medical education have a responsibility to prepare a physician workforce that can serve increasingly diverse communities, encourage healthy changes in patients, and advocate for the social changes needed to advance the health of all. The authors of this Perspective discuss many of the likely causes of the observed differences in mean Medical College Admission Test (MCAT) scores between students from groups well represented in medicine and those from groups underrepresented in medicine. The lower mean MCAT scores of underrepresented groups can present challenges to diversifying the physician workforce if medical schools only admit those applicants with the highest MCAT scores. The authors review the psychometric literature, which showed no evidence of bias in the exam, and note that the differences in mean MCAT scores between racial and ethnic groups are similar to those in other measures of academic achievement and performance on high-stakes tests.