Neutron activation analysis and instrumental Ge(Li) gamma-spectrometry were used to determine the amounts of 33 elemental constituents in the heart tissue of rats. A fast ion-exchange group separation sceme was developed for confirmation of the quantitative and qualitative results. The results, in parts per million of dry heart tissue, are given for 26 elements, together with some typical gamma-spectra at various irradiation and decay times. Optimum irradiation and decay periods for the various components are suggested.