The 2-hour long United Kingdom Clinical Aptitude Test (UKCAT) is used by many universities in the United Kingdom as part of their selection process for undergraduate medical and dentistry degrees. We aimed to compare the performance of senior doctors in primary and secondary care and across a range of specialties, in a modified version of the medical school entrance examination-the mUKCAT. Lay people were also included in the study. Despite its widespread use, this is the first study that examines the performance of senior clinicians in the UKCAT.The study used a prospective cross-sectional design. It used mock questions from the UKCAT website to generate an mUKCAT that was anticipated to take 15 minutes to complete. In all, 167 doctors at consultant, general practitioner (GP), or specialty trainee grade and 26 lay people took part.The overall mean mUKCAT score of all participants was 2486 (69.1%). Of the total cohort, 126 (65.3%) scored above our designated threshold of 2368 and were deemed to have passed the mUKCAT. Excluding lay people, 113 (67.7%) of the 167 doctors scored above that threshold. Medical specialty was associated with overall score (P = 0.003), with anesthetists/intensive care physicians scoring highest (n = 20, mean score 2660) and GPs scoring lowest (n = 38, mean score 2302). Academics outperformed nonacademics (mean score of academics, n = 44 vs nonacademics, n = 123: 2750 vs 2406; P < 0.001). Those clinicians in senior management positions scored lower than those in "standard" roles (mean score of senior management, n = 31 vs standard roles, n = 136: 2332 vs 2534, mean difference 202, 95% confidence interval 67-337, P = 0.004).In the situational judgement section, there was no evidence that specialty was associated with score (P = 0.15). Academics exhibited greater situational judgement than their nonacademic colleagues (academics vs nonacademics: 69.8 vs 63.6%; P = 0.01).The majority of senior clinicians passed our mUKCAT. Academics and anesthetists were found to be the best performers, with GPs and those in senior management positions performing the worst.