Attenuation measurements have been made on liquid argon for temperatures between 90 and 150 °K and pressures between saturated vapor and 1000 p.s.i. Values of bulk viscosity were calculated and compared with theoretical results. For densities above 1.15 gcm−3 the PNM theory is in excellent agreement. However, below these values the theoretical results continue to decrease with density where the experimental results increase sharply. The values of the ratio of bulk to shear viscosity for saturated vapor pressure are found to be a linear function of (Tc–T)−3/2 from 90 to 140 °K.