A 77-year-old male presented with an abdominal aortic aneurysm (AAA). He underwent preoperative cardiopulmonary exercise testing (CPET) to help assess his suitability and fitness for complex major vascular surgery. His aneurysm subsequently ruptured in the post-test period and he underwent emergency open repair. CPET is a useful tool in the repertoire of anaesthetic pre-assessment and helps inform decision-making in high-risk surgical patients. However any single test has its limitations and it should not be used in isolation as a reason to deny a patient surgery. Patients with a diagnosed AAA should not forgo CPET for fear of rupture but should be closely monitored for signs of rapid uncontrolled hypertension - an indication to terminate the test early.