The coefficients of absorption of high intensity ultrasonic waves in liquids (carbon tetrachloride and water) have been measured as a function of intensity. The absorption coefficient increases by a factor of 5 for water and 2 for carbon tetrachloride for intensities of about5 watts/cm2. The increase is attributed to wave form distortion of a wave of finite amplitude. A theory is developed in which the medium is treated as the acoustical analog of a transmission line with nonlinear elements. The theory enables one to follow the details of the change of an initially sinusoidal wave of finite amplitude, in a dissipative medium, in to a “comparatively” stable distorted wave form that eventually returns to an infinitesimal sinusoidal wave. Quantitative agreement of theory is obtained with experiment for the distance needed for comparative stabilization, the growth of harmonic content in the distorted wave, and the details of the absorption process.