Objectives : This study was conducted to investigate the activity of the supra and infrahyoid muscles according to the temperature and the amount of water in healthy adults. Methods : The amount of water was set to 3 mL and 20 mL, and the temperature was subdivided into 4 ℃, 22 ℃, and 40 ℃ in order to compare the activity of the supra and infrahyoid muscles in twenty-seven healthy adults. We used the mean value of the activity of the supra and infrahyoid muscles while they were swallowing saliva in order to set the reference voluntary contraction (%RVC). Results : Muscle activity was significantly increased when they swallowed 20 mL of water rather than 3 mL in the left infrahyoid muscles at 4 ℃, 22 ℃ and 40 ℃ (p=.00; p=.00; p=.00), the right infrahyoid muscles at 22 ℃and 40 ℃ (p=.01; p=.01), the left suprahyoid muscles at 4 ℃ (p=.03). Muscle activity of the right suprahyoid muscles was significantly decreased at 40 ℃ compared to 4 ℃ and 22 ℃ when they swallowed 20 mL of water (p=.04). Conclusion : In the future, other variables such as viscosity and taste should be considered, and further studies on patients with impaired nervous system as well as healthy subjects will be needed.