Five new and two known species belonging to the family Aulolaimoididae are described and illustrated from India and Costa Rica. Adenolaimus minor sp. n. is characterised by the short body (L = 0.38-0.46 mm), stoma supported by minute ribs, monoopisthodelphic female genital system with a small pre-uterine sac, obtusely rounded tail and male with slender spicules. Adenolaimus loofi sp. n. is characterised by the 0.66-0.72 mm long body; stoma and pharyngeal walls supported by minute rib-like structures; truncate lip region; 4.0 μ m long odontostyle; odontophore with basal flanges; mono-opisthodelphic female genital system with anterior uterine sac 0.7-1.0 times corresponding body diam. long; short hemispheroid tail and males with two, spaced, ventromedian supplements. Adenolaimus clavatus sp. n. is characterised by the 0.90-1.01 mm long body; stoma and pharyngeal walls supported by minute rib-like structures; continuous, rounded, lip region; 5.5-6.0 μm long odontostyle; odontophore with basal flanges; mono-opisthodelphic female genital system with a small anterior uterine sac and short clavate tail. Adenolaimus tropicus sp. n. is characterised by the 0.75-0.80 mm long body; lip region rounded and offset by depression; 5 μm long odontostyle; pharyngeal bulb not constricted; anterior genital branch reduced to an uterine sac and short hemispherical tail. Oostenbrinkia parva sp. n. is characterised by the small body (L = 0.440.49 mm); 4.0 μm long odontostyle with forked base, flanged odontophore; post-median vulva; vagina with two slender sclerotised pieces; amphidelphic genital system and short, hemispheroid, tail. Two known species, Aulolaimoides elegans and Adenolaimus orthus are redescribed and the generic diagnosis of Oostenbrinkia is emended. A species compendium and key to the genera and species of Aulolaimoididae are provided.