This book provides basic information and different protocols associated with the Entomopathogenic nematodes (EPNs) and their symbiotic bacteria. Entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis and their associated bacterial symbionts Xenorhabdus and Photorhabdus aid nematode infective juveniles (IJs) in infecting and killing their insect hosts, creating a unique tripartite complex of host-vector-symbiont interactions. Due to this insect killing capability, EPNs are used as biological control agents of economically important insect pests. They are also a model system to study host-parasite interactions. It provides a systematic approach to various nematode procedures including pathogenicity, reproduction, foraging behaviour. It gives a brief outline on historical aspects, nematode-bacterium complex, biology and chemical ecology of EPNs. It concisely describes host insect rearing, nematode samplingand storage, isolation techniques, counting, handling and staining of nematodes, characterization including morphological, molecular and ecological studies, mass production, virulence bioassay, field application and efficacy. The book also includes methods and techniques for their associated symbiotic bacteria. This book serves as a laboratory manual and assists the readers to undertake advanced research in different aspects related to nematodes. It is useful for researchers in the fields of nematology, microbiology, bacteriology and entomology.