To improve the efficiency of the public sector, a decentralization process has been engaged in a large number of developing countries. This thesis, in four parts, analyzes various aspects of decentralization in developing countries. Part 1, which consists in a review of literature, studies the expected theoretical effects of decentralization, examines their relevance in the particular context of developing countries and, draws up a critical assessment of empirical studies evaluating the existence of such effects (chapter 1). Part 2 focuses on the relevance of an essential argument in favor of decentralization, largely ignored in studies on developing countries: the "competition principle". More precisely, we analyze the existence of strategic interactions between local governments in a context of weak fiscal resources (case of Benin, chapter 2) and in the absence of local democracy (case of China, chapter 3). Part 3 relates to the vertical relationship between the central government and local governments. In particular, we focus on the effect of central fiscal transfers on the level of local own-Revenue in Benin (chapter 4) and on the determinants of the allocation of fiscal transfers between local governments in Senegal (chapter 5). Finally, in part 4, we determine the average and distributional impacts of decentralization on the access to basic services by local population (chapter 6).