A method of neutron activation analysis (NAA) for the determination of Cs inside a thin Pd electrode deposited on a Pt or Au matrix is reported. This simple and rapid method involves a post-irradiation radiochemical separation of Cs from high activities of interfering radionuclides. The separated Cs was determined by high resolution -ray spectrometry. The method allows the determination of Cs without a time-consuming cooling period. The radiochemical procedure (RNAA) is found to be relatively highly precise, sensitive, rapid and simple. Pre-irradiative chemical separation of Cs is likely to be reasonable.