H-1 NMR spin-lattice relaxation times (T-1) of water, methanol, and ethanol (abbreviated as W.M.E) were measured in the range of 25 to 400 degrees C at 30, 20, and 20 MPa, respectively by using high-pressure NMR. It was found that the T-1 values for each group of W.M.E increase with an increase in temperature up to around 220, 160, and 170 degrees C, and that above these temperatures, the T-1 values decrease and approach a constant value at 300, 200, and 220 degrees C, respectively. It is explained that the spin-lattice relaxation (SLR) processes are dominated by the dipole-dipole (DD) mechanism at lower temperature and by the spin-rotation (SR) mechanism at higher temperatures. The reasons that the T-1 values are nearly constant are supposed.