Background: The current and projected health worker shortage crisis in low and middle-income countries (LMIC) requires that effective strategies for expanding the numbers of health workers be quickly identified in order to inform action by policy makers, educators and health planners. Objectives: To assess the effect of changes in the pre-licensure education of health professionals on health worker supply. Methods: We searched EMBASE, MEDLINE, CENTRAL and CINAHL on 1610/07, LILACS (29/11/07), ERIC (12/02/08), Sociological Abstracts (19/10/07). We searched WHO (WHOLIS), World Bank, Google Scholar, human resources for health related websites for grey literature. Key experts in human resources for health were contacted to identify unpublished studies. Reference lists of included studies were searched. Criteria: Randomized clinical trials, non randomized clinical trials, controlled before and after studies, and interrupted time series studies that measured increased numbers of health workers ultimately available for recruitment into the health workforce or improved patient/health professional ratios. Quality assessment of the studies was based on the Cochrane Handbook for Systematic Reviews of Interventions guidelines. Results: Two studies out of 7880 identified from electronic databases met the inclusion criteria. Both were controlled before and after studies exploring the effect of interventions to improve retention of minority groups in health professional training institutions. Other studies outside our inclusion criteria offered potential insights on existing strategies and the impact of educational policies on health worker supply. For instance, the provision of training funds in the form of educational subsidies was positively associated with increased supply of nurses as were interventions to facilitate recruitment of students through the provision of additional academic support and mentorship. Conclusions: Evidence to estimate the likely effects of interventions in prelicensure education to increase health worker supply is insufficient. Promising innovations from high income countries include identifying/encouraging potential students and offering support to ‘at risk’ students. However, the degree to which these can be successful in LMICs needs to be explored and evaluated. It is also evident that any intervention selected will require massive funding and collaboration between policy makers, donors, health planners and training institutions.