SUMMARYThis review summarises the present knowledge concerning the decomposition by selflirradiation of compounds labelled with the radioisotopes, carbon-14, hydrogen-3 (tritium), sulphur-35, selenium-75, chlorine-36, phosphorus-32, iodine-125, iodine-131, cobalt-57 and cobalt-58. A discussion of the methods which can be used for the control of this decomposition is also included.