The thermal relaxation absorption in carbon disulfide vapor at temperatures between 0° and 160°C has been obtained for frequencies between 50 kc and 4 Mc per sec per atm. The data were obtained by the tube method. The relaxation time, the transition probability, and the collision efficiency were determined as a function of temperature from the measured data. The collision efficiency as a function of temperature is adequately predicted by the Landau and Teller theory.