Book excerpt: This thesis focuses on the sustainability issues in health financing in low-and middle -income countries. It is articulated around four chapters. The two first chapters propose to respectively explore the determinants of technical efficiency of health expenditures and their level per capita in low-and middle -income countries. The first chapter analyzes trade openness effect on the technical efficiency of health expenditures. The second chapter investigates air pollution effect on health expenditures. In the two last chapters, we focus on Sub-Saharan African countries. The third chapter studies the role that plays prepayment health financing for health improvement in households whereas the fourth one sets the goal to analyze the determinants of prepayment health expenditures, by particularly focusing on political instability.