Thesis: This dissertation aims at better understanding the determinants of individual health status. It focuses both on determinants of health investments and external factors impacting directly the health status. The dissertation is divided into three chapters. Chapter 2 focuses on determinants of the demand for prevention among elderly. During last years, the Retirement Insurance has increased prevention supply, in particular for housing adaptation but the take-up for the program still remains very low. We implement a large eld experiment with several incentives in order to determine the nature of demand-side barriers for prevention. We provide evidence that providing information is the main fruitful policy avenue. Chapter 3 evaluates the impact of an information campaign on health demand in Mali. The campaign did not take place in all Malian health districts at the same time and was therefore realized in three waves. We exploit these temporal exogenous variations in order to evaluate the impact of the campaign on health demand. We nd that providing information has a strong impact on assisted childbirth and prenatal care rates. Chapter 4 points out that the working environment could lead to large consequences on the health status, in particular on the psychological dimension. We overcome methodological problems linked to endogeneity issues by exploiting the exogenous change of the European legislation that aimed at increasing competition in the energy market. We use unique panel data on workers and provide evidence that organizational changes caused a deterioration of the workers' health outcomes.