A computerized approach to the average absorbed dose calculations in the standard human body is reported. For each selected radionuclide, a matrix S of the order n X n is constructed and stored in the computer. The matrix elements consist of the absorbed dose coefficients per unit cumulated activity (rad microCi-1 hr-1) for n different organs. Each element Sij of the matrix S represents the average dose contribution from a particular radionuclide uniformly distributed in the source organ j to the target organ i. Therefore, the diagonal elements of S represent the average absorbed dose contribution from each organ to itself (target to target). The different organ uptake coefficients and the biological half-lives of several elements and compounds gathered from the literature were organized and stored on the computer disk. During dosimetry evaluations, the system retrieves the physical half-life of the involved radionuclide, searches for the appropriate biophysical factors, computes the cumulated activities Ai of the n organs and then constructs the cumulated activity vector A. The estimates of the average dose absorbed in the various targets are presented by the organ dose vector D. Hence, the dosimetry evaluations of all organs may be obtained by simply multiplying the matrix S by the column vector A.