The Family Thelastomidae (Thelastomatoidea; Oxyurida; Nematoda) is revised, genera are diagnosed and a complete list of species is given. The following genera, normally classified in the family, are not included: Linstowiella Basir is considered a member of the Pharyngodonidae and perhaps a synonym of Pharyngodon Diesing; Klossinema Lal is considered a synonym of Cephalobellus Cobb; Schubartnema Kloss is considered a taxonomic chimaera, the male corresponding to Carnoya Gilson and the female probably to Binema Basir. Two new species are proposed: Gryllophila bainae and G. klossae for material assigned to G. skrjabini (Sergiev) by Bain (1965) and Kloss (1959) respectively. The following new synonyms are proposed: Blattellicola Basir and Blatellicoloides Farooqui synonyms of Blatticola Schwenck;