A number of low- and middle-income countries have a severe shortage of health workers. This paper studies how health workers' choices of labour supply and work effort impact on the quality of health services when health workers are in short supply. We analyse how policy measures such as monetary incentives, monitoring, provisions of quality-enhancing inputs, and the building of professionalism and organizational identity can improve the quality of health care in the presence of a health worker shortage. We find that to pay health workers based on the number of patients may have a positive impact on the quality of health care even if quality does not affect demand. Furthermore, provision of quality-enhancing drugs and equipment may reduce health workers' effort in delivering quality care, thus diminishing the positive impact of such interventions. Our most surprising result is that if the actual quality of health care is far below a professional standard, measures to build a professional mindset among health workers may reduce the quality of care.