This book is a compilation of the systematics of the genus Diphtherophora (Nematoda: Diphtherophoridae) including all 37 currently accepted species which are reported worldwide. These nematodes are soil inhabitants, occur mostly in the vicinity of plant roots. For each species, morphometric data, descriptions of females and males, relationships with close species, and their distribution are discussed. The book is amply illustrated with drawings and photomicrographs obtained from microscopic observations. Identification key and diagnostic compendium to the species are included. The morphology of the family Diphtherophoridae is treated in detail, with emphasis on the diagnostic characters used for reliable identification. This book hopefully will help students, nematologists and other interested academic disciplines especially with the identifications to species level.