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Nematodes in the genus Abbreviata (Physalopteridae) were the dominant gastrointestinal helminths in the eight smallest species of dwarf varanid lizards (subgenus Odatria, Varanidae). All host species supported infection with encysted physalopterid larvae, which provoked minimal pathological changes in the host. The mean number of cysts in host tissues increased with host size across species. There were moderate prevalences of infection of adult A. hastaspicula in Varanus (O.) brevicauda (50%) and V. (O.) storri (32%), and of A. levicauda in V. (O.) pilbarensis (46%). There were no adult Abbreviata sp. infections in V. (O.) bushi. Intensity of infection was low in almost all hosts. Sympatric larger species of Varanus (subgenus Varanus) (V. gouldii, V. panoptes, and V. (O.) tristis) support heavy infections of these nematodes which may be a source of infection for dwarf varanids. The presence and species of adult Abbreviata in dwarf monitors could not be related to sympatry, host size, or host geographical range. Liability to infection is probably determined by a combination of phylogeny (in A. levicauda in V. pilbarensis and V. tristis, dwarfism being derived), and habitat (A. levicauda occurring in other arboreal species). Other facets of the physiology or ecology, not yet understood, are also probably involved. This study reveals a complex situation where evolutionary history and contemporary environments interact. Physalopteroides filicauda, Maxvachonia brygooi, Wanaristrongylus ctenoti, Hastospiculum gouldi, the cestode Oochoristica vacuolata, and a species of pentastomid were also recovered in low numbers.