The effects of presumptive radiation protective compounds have mainly been ivestigated only with respect to their influence on the survival rate but seldom as regards physiologic effects before, during and after irradiation. Neither have their negative effects been considered, sometimes due to the absence of suitable methods. Criborn (1969, 1970) presented methods concerning the determination of respiratory minute volume, oxygen consumption and respiratory response to acoustic excitation. A number of compounds with proved radiation protective effects were found to depress the oxygen consumption and respiratory response strongly during their active phase. In the present investigation the depressive effect of cysteamine on these parameters was stimulated by the use of some psychopharmaca. Attempts were made (1) to decrease the effect of cysteamine on respiration and body temperature by using a central stimulating compound, amphetamine, and (2) to correlate the effects of these compounds to a change in the radiation protective effect of cysteamine. This would give a more differentiated evaluation of the effect of presumtive radiation protective compounds.