The purpose of this study is to assess the variability in grading systems used by US allopathic and osteopathic medical schools across all 4 years of medical school coursework. Transcripts were reviewed from all participating allopathic and osteopathic medical schools for all 4 years of coursework for grading system type, the presence or absence of a key or guide, the inclusion of grade distribution within class year, inclusion of a class rank, and summary statements or evaluation systems used by the institution within the Medical Student Performance Evaluation to evaluate overall performance. Loyola University Medical Center. Maywood, IL. Transcripts were reviewed for 144 out of existing 147 allopathic medical schools (97.9%) and 37 out of 39 existing osteopathic medical schools (94.8%). For allopathic schools, grading system distribution for preclinical years was-41.6% Pass/Fail, 40.3% Honors, 13.2% Letter; while grading system distribution for clinical years was-78.5% Honors, 15.9% Letter. Only 35.4% of allopathic medical schools used the same system for all 4 years, while the remaining schools used a different system for preclinical and clinical years. For osteopathic medical schools, grading system distribution for preclinical years was-45.9% Letter, 32.4% Honors, and 13.5% Pass/Fail; while grading system distribution for clinical years was-59.5% Honors and 29.7% Letter (Table 4). Overall, 56.7% of osteopathic programs used the same system for all 4 years, while the remaining schools used a different system for the preclinical years than the clinical years. Variability also existed within each of these broader grading system categories (Table 1, Table 3). Our results highlight the variability in grading systems used by medical schools both among programs and between preclinical and clinical years. From the residency program perspective, the lack of consistent, objective comparisons between school transcripts makes comparing applicants from different institutions difficult.