The normal modes of myoglobin, their lifetimes, the speed of sound, and mean free path are calculated to determine the coefficient of thermal conductivity and thermal diffusivity for the protein. A propensity is found for frequency differences of pairs of normal modes localized to nearby regions of the protein to be several hundred cm(-1). As a result, the anharmonic decay rate of higher frequency, localized normal modes, calculated by perturbation theory, is typically nearly independent of temperature. consistent with results of pump-probe studies on myoglobin. The thermal diffusivity of myoglobin at 300 K is calculated to be 14 Angstrom(2) ps(-1), the same as the value for water. The thermal conductivity at 300 K is found to be 2.0 mW cm(-1) K-1, about one-third the value for water.