The present work includes a comprehensive study on soil & plant parasitic nematodes belonging to the orders Dorylaimida & Tylenchida associated with guava & Litchi plantations in India. Nematodes are considered as one of the major constraints in agriculture & horticulture allover the world & are responsible for yield losses of guava & litchi. The taxonomic part comprises of identification of the available specimens up to species level. It provides information on nematode association of these cash crops which is important globally. The ecological part includes the monthly population fluctuation. As the different edaphic factors, like soil moisture, temperature, pH, nitrogen, phosphorus, potassium, organic carbon & soil electrical conductivity are the determining factors for the shape and quality of the nematode population in soil micro-environment, the effects of these soil factors on nematode population have been investigated. The effectiveness of predatory and omnivorous nematodes as a bio-controlling agent to reduce the population of tylenchids was tested statistically. The present effort may contribute some additional and valuable information on this relatively unattended field.