蘭科石斛屬植物的莖是一種名貴的中草藥，因此時常有偽品出現造成混淆，因此鑑定真偽品的方法是一個必要的課題。在本研究中，以Internal Transcribed Spacers（ITS）的分析來確定11種石斛及兩個偽品（Pholidofa articulata and Fickingeria comate）的親緣關係。結果顯示，13個物種ITS總長度介於635至641bp，其GC含量（ITS1+5.8S+ITS2）的50.55%至57.25%。石斛屬ITS序列之間約有平均13.20%的差異，而石斛與P. articulata and F. comate則分別有42%和29.00%的差異。分子演化樹顯示，石斛屬遺傳距離較為接近，而偽品距離較遠並各自獨立。因此，ITS是一種可以被用於鑑別藥用石斛的分子標記。

Herba Dendrobii, commonly known as "Shi-hu", has been used as a precious traditional Chinese medicine. It is expensive and adulteration arc common due to high demand. The method to distinguish the herb from adulterant species is necessary. In the present study, internal transcribed spacers (ITS) region-based analysis was employed to ascertain the phylogenetic relationship among the 11 Dendrobium and two adulterant species Pholidota articuluta and Flickingeria comate. Results showed that the length of the ITS regions among the thirteen species ranged from 635 to 641 bp and the GC ratio in ITS (ITS1+5.8S+ITS2) regions ranged from 50.55% to 57.25%. Dendrobium species was significantly different from one another by an average of 13.20% and from P. articulata and F comate by 42.00 % and 29.00% respectively. The molecular phylogenetic trees indicated that most of Dendrobium species are closely related and share common clad while both the adulterants outgroup and have separated clad. Therefore, ITS regions can be used as a molecular marker to differentiate medicinal Dendrobium spp. from one another and also from adulterants.