Achromadoridae Gerlach & Riemann, 1973 (taxonomy source)
Aegialoalaimidae Lorenzen, 1981 (taxonomy source)
Alaimina (taxonomy source)
Alaimoidea Micoletzky, 1922 (taxonomy source)
Anoplostomatidae Gerlach & Riemann, 1974 (taxonomy source)
Anticomidae Filipjev, 1918 (taxonomy source)
Aphanolaimidae Chitwood, 1936 (taxonomy source)
Aponchiidae Gerlach, 1963 (taxonomy source)
Aporcelaimidae Heyns, 1965 (taxonomy source)
Araeolaimida (taxonomy source)
Aulolaimidae Jairajpuri & Hopper, 1968 (taxonomy source)
Axonolaimidae Filipjev, 1918 (taxonomy source)
Bastianiidae De Coninck, 1965 (taxonomy source)
Benthimermithida accepted as Plectida (taxonomy source)
Benthimermithidae Petter, 1980 (taxonomy source)
Bradylaimus Stekhoven, 1931 (new combination reference)
Camacolaimidae Micoletzky, 1924 (taxonomy source)
Campydoroidea Thorne, 1935 (taxonomy source)
Ceramonematidae Cobb, 1933 (taxonomy source)
Ceramonematina (taxonomy source)
Chromadorida (taxonomy source)
Chromadoridae Filipjev, 1917 (taxonomy source)
Chronogastridae Gagarin, 1975 (taxonomy source)
Comesomatidae Filipjev, 1918 (taxonomy source)
Coninckiidae Lorenzen, 1981 (taxonomy source)
Cyatholaimidae Filipjev, 1918 (taxonomy source)
Desmodorida (taxonomy source)
Desmodoridae Filipjev, 1922 (taxonomy source)
Desmodoroidea Filipjev, 1922 (taxonomy source)
Desmoscolecida (taxonomy source)
Desmoscolecidae Shipley, 1896 (taxonomy source)
Desmoscolecoidea Shipley, 1896 (taxonomy source)
Dioctophymidae Railliet, 1915 (taxonomy source)
Dioctophyminae Railliet, 1915 (taxonomy source)
Diplopeltidae Filipjev, 1918 (taxonomy source)
Diplopeltoididae Tchesunov, 1990 (taxonomy source)
Dorylaimia (taxonomy source)
Dorylaimidae de Man, 1876 (taxonomy source)
Dorylaimina (taxonomy source)
Draconematidae Filipjev, 1918 (taxonomy source)
Enchelidiidae Filipjev, 1918 (taxonomy source)
Enoplea (taxonomy source)
Enoplia (taxonomy source)
Enoplida (taxonomy source)
Enoplidae Dujardin, 1845 (taxonomy source)
Enoplina (taxonomy source)
Enoploidea Dujardin, 1845 (taxonomy source)
Epsilonematidae Steiner, 1927 (taxonomy source)
Ethmolaimidae Filipjev & Schuurmans Stekhoven, 1941 (taxonomy source)
Eustrongylides Jägerskiöld, 1909 (taxonomy source)
Haliplectidae Chitwood, 1951 (taxonomy source)
Ironidae de Man, 1876 (taxonomy source)
Ironina (taxonomy source)
Ironoidea de Man, 1876 (taxonomy source)
Leptolaimidae Örley, 1880 (taxonomy source)
Leptosomatidae Filipjev, 1916 (taxonomy source)
Linhomoeidae Filipjev, 1922 (taxonomy source)
Linhomoeina (taxonomy source)
Metachromadoroides Timm, 1961 (new combination reference)
Meyliidae De Coninck, 1965 (taxonomy source)
Microlaimidae Micoletzky, 1922 (taxonomy source)
Microlaimoidea Micoletzky, 1922 (taxonomy source)
Monhysterida (taxonomy source)
Monhysteridae de Man, 1876 (taxonomy source)
Monhysterina (taxonomy source)
Monhysteroidea Filipjev, 1929 (taxonomy source)
Mononchida (taxonomy source)
Mononchidae Filipjev, 1934 (taxonomy source)
Mononchina (taxonomy source)
Monoposthiidae Filipjev, 1934 (taxonomy source)
Neotonchidae Wieser & Hopper, 1966 accepted as Ethmolaimidae Filipjev & Schuurmans Stekhoven, 1941 (taxonomy source)
Odontolaimidae Gerlach & Riemann, 1974 (taxonomy source)
Oncholaimidae Filipjev, 1916 (taxonomy source)
Oncholaimina (taxonomy source)
Oncholaimoidea Filipjev, 1916 (taxonomy source)
Oxystominidae Chitwood, 1935 (taxonomy source)
Pandolaimidae Belogurov, 1980 (taxonomy source)
Paramicrolaimidae Lorenzen, 1981 (taxonomy source)
Phanodermatidae Filipjev, 1927 (taxonomy source)
Plectida (taxonomy source)
Plectidae Örley, 1880 (taxonomy source)
Plectina (taxonomy source)
Plectoidea Örley, 1880 (taxonomy source)
Prismatolaimidae Micoletzky, 1922 (taxonomy source)
Qudsianematidae Jairajpuri, 1965 (taxonomy source)
Rhabdodemaniidae Filipjev, 1934 (taxonomy source)
Rhadinematidae Lorenzen, 1981 (taxonomy source)
Selachinematidae Cobb, 1915 (taxonomy source)
Siphonolaimidae Filipjev, 1918 (taxonomy source)
Siphonolaimoidea Filipjev, 1918 (taxonomy source)
Sphaerolaimidae Filipjev, 1918 (taxonomy source)
Sphaerolaimoidea Filipjev, 1918 (taxonomy source)
Tarvaiidae Lorenzen, 1981 (taxonomy source)
Thoracostomopsidae Filipjev, 1927 (taxonomy source)
Triodontolaimidae (De Coninck, 1965) Hope & Murphy (taxonomy source)
Triplonchida (taxonomy source)
Tripylidae de Man, 1876 (taxonomy source)
Tripyloidina (taxonomy source)
Tripyloidoidea Filipjev, 1928 (taxonomy source)
Tubolaimoididae Lorenzen, 1981 (taxonomy source)