Abstract: Chen Shanshan, Zhou Jianfeng, Liao Yong, Li Haitao, Wang Ruili, Ba Gen, Lyu Xuelian, Yang Rongya Department of Dermatology, General Hospital of Beijing Military Command, Beijing 100700, China Corresponding authors: Yang Rongya, Email: yangrya@sina.com; Lyu Xuelian, Email: mycoses@gmail.com 【Abstract】 Objective To investigate differences in the of Ras1, Rac1 and Rho1 genes between yeast and hyphal phases of Trichosporon asahii （T.asahii）, and to explore their roles in the formation of hyphae. Methods The yeast phase and hyphal phase of T.asahii were cultured and served as yeast phase group and hyphal phase group respectively. Total RNA was extracted from the 2 groups, and real?time fluorescence?based quantitative PCR （RT?PCR） was performed to measure the mRNA of Ras1, Rac1 and Rho1. Results The hyphal formation rate was significantly lower in the yeast phase group than in the hyphal phase group （0.40% ± 0.53% vs. 99.33% ± 0.57%, t = 13.93, P < 0.05）. When the mRNA of Ras1, Rac1 and Rho1 in the yeast phase group was all set as 1, that in the hyphal phase group was 25.17 ± 10.99, 16.81 ± 7.80, 42.61 ± 18.50, respectively, with significant differences between the two groups in the three parameters （t = 3.81, 3.51, 3.90, respectively, all P < 0.05）. Conclusion Ras1, Rac1 and Rho1 genes may participate in the regulation of hyphal formation in T.asahii.