The opposing forces of increased training expectations and reduced training resources have greatly impacted health professions education. Virtual patients (VPs), which take the form of interactive computer-based clinical scenarios, may help to reconcile this paradox. We summarise research on VPs, highlight the spectrum of potential variation and identify an agenda for future research. We also critically consider the role of VPs in the educational armamentarium. We propose that VPs' most unique and cost-effective function is to facilitate and assess the development of clinical reasoning. Clinical reasoning in experts involves a non-analytical process that matures through deliberate practice with multiple and varied clinical cases. Virtual patients are ideally suited to this task. Virtual patients can also be used in learner assessment, but scoring rubrics should emphasise non-analytical clinical reasoning rather than completeness of information or algorithmic approaches. Potential variations in VP design are practically limitless, yet few studies have rigorously explored design issues. More research is needed to inform instructional design and curricular integration. Virtual patients should be designed and used to promote clinical reasoning skills. More research is needed to inform how to effectively use VPs.