Nematodes are the most numerous metazoans in aquatic sediments. The majority of conducted studies on these aquatic forms focus mainly on those in marine and estuarine habitats. Nematodes from inland water bodies have been relatively forgotten or ignored. Recognizing this serious drawback and its impact on research on nematodes, this book brings together the available information on freshwater nematodes. It addresses the taxonomy of this extremely diverse phylum and provides analysis of its ecology in freshwater habitats from nematologists from 12 countries worldwide. Descriptions of each taxon at genus-level and above are provided with an augmenting pictorial guide to the currently valid genera. Also, a complete, up-to-date and valid species-list is given for every genus with an emphasis on those reported from freshwater bodies.