Two, morphologically indistinguishable myxosporean species, Myxobolus elegans Kashkovsky, 1966 and M. hungaricus Jaczó, 1940 were differentiated using molecular biological methods. Polymerase chain reaction (PCR) with primers specific for the family Myxobolidae was used to amplify an approximately 1600 base pairs (bp) long fragment of the 18S ribosomal RNA gene. In restriction fragment length polymorphism (RFLP) study with HinfI, MspI and TaqI enzymes, the two parasite species were easily distinguishable. The genetic distinctness was also confirmed by the DNA sequence of their PCR products. Although M. elegans and M. hungaricus are morphologically very similar, based on the results of the PCR-RFLP and the DNA sequences, we concluded that they are valid species.