Conventional wisdom says that, because low-income countries need skilled professionals to develop, their migration to better-paying countries is unequivocally bad--when they leave, poor countries lose engineers' ideas, lawyers' contracts, and physicians' care. So the recent surge in the international mass migration of highly skilled workers has many worrying: will the loss of skilled professionals stymie development? In this new working paper, CGD research fellow Michael Clemens uses new data on African health worker migration to test whether decreases in emigration raise the number of domestic health professionals, increase the mass availability of basic primary care, or improve a range of public health outcomes. The results suggest that Africa's generally low staffing levels and poor public health conditions are the result of factors entirely unrelated to international movements of health professionals, and that the option to emigrate has positively affected Africans' decisions to enter the health field. Bottom line: impeding the migration of skilled health professionals, by sending and receiving countries, does little to improve health systems or heath outcomes in Africa.