A parasitological survey of aquatic hymenochirine toads (Pipidae) from tropical Africa indicated the occurrence of camallanid larvae in these hosts is a regula ecological phenomenon. Pseudhymenochirus merlini at one site in western Sierra Leone was infected by third-stage larvae of a Camallanus species occurring in the intestine. Third- and fourth-stage larvae of a distinct Camallanus species occurred in the stomach and intestine of P. merlini at another locality, also in western Sierra Leone. An imported pet trade consignment of Hymenochirus curtipes from Nigeria contained third-stage procamallanine larvae, some of which showed morphological changes preceding the third moult. Comparable specimens occurred in museum collections of H. boettgeri from the Democratic Republic of the Congo. Procamallanines wee localised in the host's stomach. The morphology of camallanid larvae recovered is described, and their possible relationships considered. Predation on hymenochirines might present an important transmission route for these parasites between copepod intermediate hosts and larger aquatic predators. However, the final hosts and their trophic relationships with hymenochirines are unknown. Regardless of its significance for transmission, the survival ability of larval stages in non-definitive host vertebrates might have predisposed camallanid lineages to evolutionary host changes and contributed to the wide dispersal of the family.