It is well known that rotational motion is strongly correlated with translational motion in polar liquids [1] and aqueous solutions of non-electrolytes [2]. The investigation on the correlation of these motions is one of the usefull approach for elucidating the structure in the mixture of polar liquids. In this report we investigate the concentration dependence of the deuteron relaxation rate 1/T 1 of the partially deuterated alcohols CD 3OH, CD 3CH 2OH, and CH 3CD 2OH and the self-diffusion coefficients in methanol–ethanol system at 25 °C. The measurements of the spin-lattice relaxation times and the self-diffusion coefficients have been performed with a spin-echo spectrometer JNM-FSE 60A and a S/N Booster JNM-3B-SB(JEOL). The resonance frequencies for 1H and 2H are 60 and 9.2 MHz, respectively. All samples were degassed and sealed. In Fig. 1 is shown the concentration dependence of the self-diffusion coefficients of methanol and ethanol in the methanol–ethanol mixture. A minimum of self-diffusion coefficient of methanol appears at higher concentration than that of ethanol. The concentration dependence of the deuteron relaxation rate 1/t 1 of CD 3OH in C 2H 5OH is shown in Fig. 2. The deuterion relaxation rate shows a maximum at 11 mol% of methanol. In the case of methanol, therefore, ▪ the self-diffusion coefficient correlates with relaxation rate. In the case of ethanol, however, both the relaxation rates of –CD 3 and –CD 2 did not show the maximum but decreased with increasing the concentration of methanol.