Stagnation-point similarity solutions of the laminar boundary-layer equations are calculated for a thermally and calorically perfect gas with Prandtl number ⅔ and viscosity proportional to a power of the absolute temperature (μ ∝ T1−α). The parameter α is varied from 0 to 0.5, and the enthalpy ratio across the boundary layer from 0.01 to 0.80. The results are closely applicable to high-temperature flows of the five inert gases. Heat-flux values predicted using these results and Amdur and Mason's viscosity calculations are compared with Rutowski's shock-tube measurements for argon. The agreement is excellent up to a stagnation temperature of 5400 °K. At higher temperatures, the experimental values gradually rise above the theoretical curve, indicating possible onset of electronic excitation and ionization effects upon the heat transfer.