Our framework is useful for structuring research on the health workforce and for identifying health-worker research issues. We describe six research issues on the health workforce: metrics to measure the capacity of a health system to deliver healthcare; the contribution of public- vs. private-sector health workers in meeting healthcare needs and demands; the appropriate size, composition and distribution of the health workforce; approaches to achieving health-worker requirements; the adoption and adaption of treatments by health workers; and the training of health workers for horizontally vs. vertically structured health systems.