The MIRD internal dose calculations have been in use for more than 15 years, but their accuracy has always been questionable. There have been attempts to verify these calculations. The experimental data and the theoretical calculations were compared for 6 source organ-7 target organ configurations. The results of the comparison indicated the existence of an agreement between measured and calculated absorbed doses, when taking into consideration the average uncertainty (16%) of the measurements, and the average coefficient of variation (10%) of the Monte Carlo calculations. What factors make the MIRD method more accurate than the ICRP method?