The Intercollegiate Membership of the Royal College of Surgeons (MRCS Parts A and B) is a mandatory postgraduate examination for all aspiring higher surgical trainees in the UK. MRCS is a critical step in determining a doctor's career pathway and has significant financial and personal implications for those who fail. It is therefore imperative that this examination is valid, fair and fit for purpose. The overall aim of this PhD was two-fold. First, to identify if any variations in performance exist at Part A and B MRCS and at any other stage of surgical training between different groups of doctors, and secondly to investigate whether MRCS performance can predict future surgical training outcomes. These are performance at national selection into higher surgical training, outcomes at the Annual Review of Competence Progression (ARCP), and performance at the Fellowship of the Royal College of Surgeons (FRCS Section 1 and 2) exit examination. The results of univariate and multivariate analyses confirm that, like other postgraduate medical examinations in the UK and around the world, differential attainment exists in the MRCS and during other stages of surgical training. Analyses also revealed that Part A score was predictive of Part B MRCS, Section 1 FRCS and Section 2 FRCS success. Furthermore, number of Part A attempts was inversely related to Part B MRCS success. Performance at Part B MRCS (score and number of attempts) was predictive of national selection score, the likelihood of an unsatisfactory ARCP outcome and Section 1 FRCS success. This doctorate supports the predictive validity of MRCS and justifies its current role, in the UK, as a mandatory component of the educational curriculum for surgical trainees. However, future research must explore the reasons behind the attainment gaps observed for different groups of doctors to ensure that this examination is fair and unbiased.