Aegialoalaimidae Lorenzen, 1981 (taxonomy source)
Alaimina (taxonomy source)
Alaimoidea Micoletzky, 1922 (taxonomy source)
Anoplostomatidae Gerlach & Riemann, 1974 (taxonomy source)
Anticomidae Filipjev, 1918 (taxonomy source)
Aporcelaimidae Heyns, 1965 (taxonomy source)
Araeolaimida (taxonomy source)
Axonolaimidae Filipjev, 1918 (taxonomy source)
Camacolaimidae Micoletzky, 1924 (taxonomy source)
Ceramonematidae Cobb, 1933 (taxonomy source)
Ceramonematina (taxonomy source)
Chromadorida (taxonomy source)
Chromadoridae Filipjev, 1917 (taxonomy source)
Comesomatidae Filipjev, 1918 (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)
Diplopeltidae Filipjev, 1918 (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)
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)
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)
Mydonomidae Thorne, 1964 (taxonomy source)
Nordiidae Jairajpuri & Siddiqi, 1964 (taxonomy source)
Oncholaimidae Filipjev, 1916 (taxonomy source)
Oncholaimina (taxonomy source)
Oncholaimoidea Filipjev, 1916 (taxonomy source)
Oxystominidae Chitwood, 1935 (taxonomy source)
Phanodermatidae Filipjev, 1927 (taxonomy source)
Plectida (taxonomy source)
Plectidae Örley, 1880 (taxonomy source)
Plectina (taxonomy source)
Plectoidea Örley, 1880 (taxonomy source)
Qudsianematidae Jairajpuri, 1965 (taxonomy source)
Rhabdodemaniidae Filipjev, 1934 (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)
Thoracostomopsidae Filipjev, 1927 (taxonomy source)
Triplonchida (taxonomy source)
Tripyloidina (taxonomy source)
Xyalidae Chitwood, 1951 (taxonomy source)