SummaryIn elvers (Anguilla anguilla) imported yearly to a fish farm in Hungary the regular occurrence of aMyxobolusinfection was recorded. The parasite produces oval or spherical plasmodia of 0.1–0.2·0.07–0.12mm in the subcutaneous and intermuscular connective tissue of the head. In each piasmodium about 200 to 400 spores develop which differ morphologically from the spores of allMyxobolusspecies known from the eel and other fishes. Based upon the characteristic location of plasmodia and spore morphology, this parasite is described as a new species,Myxobolus kot