In this study the length of ITS2 from four species of the Ulvaceae in Jeju Island varied between 167 and 203 bp. The resuits of this investigation showed that two genus, Ulva and Enteromorpha are grouped in a monophyletic assemblage with 100% bootstrap support in all phylogenetic trees. However, a thorough eamination of these characters from representatives does not provided a way to identify any unique morphological features of clasdes in this tree. This study reveals that Ulva conglobata and Ulva pertusa belong to one clade in the phylogenetic tree with the samples from Jeju Island, Korea.