Abstract: The sequences of the ITS regions and 5.8S coding region of nuclear ribosomal DNA from the genus Tetrathyrium and the related genera of Hamamelidaceae were determined and analysed. Based on the ITS sequences, the phylogeny of Hamamelidoideae was reconstructed, which was similar to Endress' system of Hamamelidaceae in 1989. It was shown that all the species of the subfamily Hamamelidoideae formed a monophyletic group in this study. However within both Hamamelidoideae and the tribe Hamamelideae, the polyphyly was indicated in the MPTs. The monophyly of the tribe Eustigmateae was strongly supported (in-cluding Eustigma, Fortunearia and Sinowilsonia ). The ITS data supported Endress' treatment of merging the tribe Distylieae and Fothergilleae too. It was suggested that the genus Hamamelis was closely related to Fothergilleae in this study. Tetrathyrium and Loropetalum {armed a monophyletic group.

Key words: Terathyium