The method developed by Baird and Bird for the measurement of relative absorption intensities has been extended to the estimation of absolute absorption intensities. The estimation of absolute intensity is based on the measurement of the ratio of modulation‐frequency component to direct component of crystal current at low microwave power levels.A preliminary test of the method has been conducted by making measurements on the intensity of the line CH3Cl35,J=0→1,F=32→52over a range of crystal currents. Measured intensities less than the calculated intensity by 15 percent to 25 percent were observed over a range of nine in crystal current, indicating that the method is at least feasible for the estimation of intensities. Even crude estimates can be extremely useful in the identification of spectral lines, and it seems likely that the method admits of much refinement in accuracy.