The purpose of the study was to examine the effect of Tencel fabrics on physiological reactions of a human body and thermal comfort under the hot environment. The 3 females subjects in their twenties were selected and a wear sensation test of the subjects was performed with four experimental ensembles made of cotton and Tencel fabrics for the study in the hot environment(3$0^{circ}C$, 70%RH). The resets of the test were summarized as follows: For the mean skin temperature, Tencel garments showed about 0.2$^{circ}C$-0.4$^{circ}C$ lower than that of the cotton garment. The temperature of the rectal was 0.2$^{circ}C$-0.4$^{circ}C$ lower for Tencel garments than that for the colon garment. In the form of ensembles, the order of rectal temperature of the subjects for both Tencel and cotton ensembles was 1>IV>III>II. In the body weight loss according to garment materials, Tencel had a lower and more uniform than the cotton Thus, it could concluded that if the perspiration took into account, garments made of Tencel can be more ideal than that of the cotton. The heart rate and oxygen consumption appeared to be proportional to each other. For the heart rate, ensemble TI and TII of Tencel were much lower than ensemble CI and CII. For whole enembles except for TIV, Tencel ensembles showed relatively better thermal sensation and comfort sensation than the cotton ensembles. In the fatigue sensation, the reactions of the subjects were “slightly fatigue” and “fatigue” for the cotton, but “neutral” and “slightly fatigue” for Tencel.