A comparison made between the results of experiment and theoretical predictions of translational dispersion in the monatomic gases argon and helium. Second‐order approximations to the dispersion are presented for the continuum theory, treating the Stokes‐Navier equations as exact, and for deductions from kinetic theory, assuming that the molecules behave as (1) elastic spheres, (2) Maxwellian molecules, and (3) molecules obeying a Lennard‐Jones type potential. Agreement between experiment and kinetic theory predictions is rather favorable in the range compared, which is at 0°C, approximately 970 kc, and down to about 2 mm Hg pressure. The increases velocity of propagation (at the lowest pressures) over that at standard conditions are 27 percent for argon and 0.6 percent for helium.