This text is a translation of "Petrologie des Laterites et des Sols Tropicaux". Laterites constitute the thick weathering mantle that covers the bedrock of old continents in the intertropical domain. Lateritic soils of Africa, South America, Asia and Australia represent one-third of the continental land mass, sustain a large part of the forest reserves of the world, and support the life of more than one-half of humanity. A large portion of the waters that flow over the continents and feed the oceans is filtered through the lateritic covers. Furthermore, the presently living and active tropical soils which constitute one of the largest compartments of the global ecosystem, are developing at the expense of ancient lateritic materials that are products of a long palaeoclimatic history. Minerals of laterites, variably hydrated, are the evidence of old climates which, more or less warm and more or less humid, are believed to have followed one another on the earth over the past 150 million years. A petrological investigation, based on study of the hydration states of the weathering minerals, seeks to establish the climatic conditions of stability or instability of lateritic mantles.