Lecithochirium musculus (Looss, 1907) is a hemiurid trematode common in Anguilla anguilla (Linnaeus, 1758) in the Mediterranean and Black Seas and the north-east Atlantic Ocean. This worm is also a parasite of a wide range of fish predators of gobiids. However, the presence of this fluke in species of the genus Conger (Cuvier, in Oken, 1817 ) is uncertain. Although there are reports of immature specimens identified as L. musculus in Conger myriaster and Conger japonicus from Japan (Yamaguti S. 1934: Jpn. J. Zool. 5: 249– 541; Ichihara A. 1974: Proc. Third Int. Congress Parasitol. 3: 1614–1615), these records require confirmation because there are several morphologically similar species with which they may be confused (Gibson D.I., Bray R.A. 1986: Bull. Brit. Mus. Nat. Hist. Zool. 51: 83–89). These authors confirm that L. musculus has not been identified accurately as a parasite of species of the genus Conger, therefore the few recordings of this worm in conger eels may actually correspond to other species. Although L. musculus has been reported as a parasite of C. conger (Artedi, in Linnaeus, 1758) in the Mediterranean Sea (cited by Radujkovic B.M., Orecchia P., Paggi L. 1989: Acta Adriat. 30: 137–187), reported as Sterrhurus musculus in the same host in the Canary Islands (Gijon-Botella H., LopezRoman R. 1989: Rev. Iber. Parasitol. 49: 137–138), and in the north-east Atlantic (Sproston N.G. 1939: Trav. Stn. Biol. Roscoff 16: 33–58), there are no definite reports of this hemiurid fluke occurring in conger eels nor are there data on the degree of parasitism in fish of the genus Conger (but see Paniagua E., Vilas R. 2001: Acta Parasitol. Port. 8: 166). In this study, we examined 156 conger eels, from the spring of 1999 to the summer of 2001. The fish were caught in the Ria de Arousa (a coastal embayment in Galicia, northwestern Spain). During this time we detected only 15 individuals obtained from six conger eels that could have been L. musculus, and of these helminths, 5 were subjected to morphometric analysis. The trematodes were stained with iron acetocarmine and mounted in Canada balsam. Comparison of the measurements made on these helminths and those made on a sample taken from A. anguilla caught in the same area are