The present paper redescribed four trematode species, which are new records for Vietnam, such as: Hemiurus arelisci Yamaguti, 1938
Stomachicola muraenesocis Yamaguti, 1934
Lecithochirium alectis Yamaguti, 1970 and Merlucciotrema praeclarum (Manter, 1934) Yamaguti, 1971 (family Hemiuridae Looss, 1899). All the trematodes are illustrated and some problems concerning their geographical distribution are discussed. H. arelisci from Scomberoides lysan (Doublespotted queenfish) is characterized mainly by seminal vesicle constricted into two portions
ecsoma well developed
pars prostatica tubular, long. Characteristic features of S. muraenesocis (host: Indian pike conger Congresox talabonoides) are body very long
ecsoma enormous
seminal vesicle oval, in hindbody
pars prostatica tubular, long
majority of uterine coils within ecsoma, normally fill less than half of ecsoma. Characteristic features of L. alectis (host: Yellow drum - Nibea albiflora) are body surface smooth
seminal vesicle in forebody
vitellarium two lateral masses, divided into three and four digiti form lobes. M praeclarum from Platycephalus indicus (Bartail flathead), Elentheronema tetradactylum (Fourfinger threadfin fish) is characterized mainly by ecsoma well developed
body surface snooth
seminal vesicle in forebody
vitelline lobes digitiform.