Abdominal aortic aneurysm (AAA) rupture is an important cause of death in adults. Currently, the only treatment for AAA is open or endovascular surgical repair. In most parts of the developed world, AAAs can be identified at an early stage as a result of incidental imaging and screening programmes. Randomized clinical trials have demonstrated that early elective surgical repair of these small AAAs is not beneficial, and an unmet clinical need exists to develop medical therapies for small AAAs that limit or prevent the progressive expansion and rupture of the aneurysm. A large amount of research is currently being performed to increase the understanding of AAA pathogenesis and ultimately lead to the development of medical therapies, such as drug-based and cell-based strategies for this disease. This Review summarizes the latest research findings and current theories on AAA pathogenesis, including discussion of the pros and cons of current rodent models of AAA, and highlights potential medical therapies for AAA, summarizing previous, ongoing and potential clinical trials of medical interventions for small AAAs. This expanding volume of research on AAA is expected to result in a range of novel medical therapies for AAA within the next decade.