The authors used random effect meta-analysis to synthesize eight mean score differences of the Part III/Level3 examinations of the National Board of Osteopathic Medical Examiners (NBOME) between osteopathic medical trainees in DO residency programs and osteopathic medical trainees in MD programs. The analysis involved 6001 trainees and all Part ill or Level 3 examinations since 1992. The average mean score difference was not significantly different from zero; however, the estimates of true effect sizes of each examination varied substantially. The findings indicate that, overall, medical knowledge of osteopathic trainees in MD and DO residency programs is compatible at the time they took the examinations. However, a large variation of effect size suggests the need for further investigation of the factors other than difference between osteopathic and allopathic training programs.