Isoparorchiid trematodes are generally encountered in the air bladder of catfishes. The genus Isoparorchis Southwell, 1931 is from the air bladder of various freshwater catfishes of India, China, Java and Australia. Elongoparorchis pneumatis Hanumantha Rao is described from the air bladder of Arius spp. from Bay of Bengal. However, the genus Pelorohelmins Fischthal and Kuntz is described from the intestine of the leiognathid Gazza minuta (Bloch) from Palawan. More recently the genus Dollfustravossosius Freitas and Koun has been erected for an isoparorchiid collected from the catfish Tachysurus grandicassis (Val.) from Brazil. The ecology and some anatomical peculiarities of these trematodes seem to be of more than passing interest. The synonymy of some of them seems evident. It would appear that Dollfustravossosius is identical to Elongoparorhcis in all respects.