The present book is a detailed assessment of the pools and fluxes of detritus in aquatic and terrestrial ecosystems. Besides presenting a comprehensive analysis of the process of detritus decomposition, the book gives an exhaustive account of the biotic and abiotic factors affecting the rate of detritus decomposition. Portrayal of the role of decomposition in nutrient cycling and delineation of the contemporary concepts of humus biosynthesis are the noteworthy features of this book. The book would be serve the needs of post-graduate students having Ecology as one of their major subject and researchers engaged in soil biology and biochemistry, soil sciences and ecosystem structure and function. The present book attempts to bring together the enormous but fragmented information and fill this lacuna. It has been designed to outline the basic and fundamental aspects of detritus and its decomposition to be understood in their right perspective and envisages to put forward a clear understanding of the current concepts of this fundamental aspect of ecology and its widening horizons.