In 15 normal volunteers the action of succinic semialdehyde (SSA), and in 24 volunteers the effect of sodium succinate (SS), on the HNA have been investigated. As a result it was found that SSA brings about some enhancement of the excitatory process in cortical - mainly verbal -activities, accompanied by subjective improvement of memory and concentration. In the other hand, the administration of SS improves the stability of cortical excitatory process and its equilibrium with cortical inhibition; and enhances the connecting activity of the verbal system. These changes parallel the subjective elevation of mood and of general tone. In the basis of this study, one may suggest that succinic acid may be a psychoenergizer. The task of further investigations is to establish the range of therapeutic activity of these compounds.