Nematodes are the most numerous multi-cellular animals in the biosphere encountered in terrestrial or aquatic ecosystems among multispecies communities and are integrated in the food chain at five trophic levels according to their feeding habits. In this book, the authors present topical research in the study of nematodes, including the biological control of animal-parasitic nematodes and plant-parasitic nematodes; resistance and virulence in plant-nematode interactions; free-living nematodes in the marine ecosystem; management and control of the Pine Wood Nematode and slug pest management through nematodes in agricultural and horticultural crops.