Electric convulsion therapy (E.C.T.) was used in the treatment of 13 women inpatients suffering from depressive symptoms. Twelve of the patients showed a significant increase in urinary excretion of 3', 5' cyclic adenosine monophosphate (cAMP) on the day of treatment, whereas four controls who received all or part of the preliminary treatment but no electric shock showed a reduction. The results of this study are consistent with the hypothesis that the antidepressant action of E.C.T. is mediated through an increased production of cAMP in brain tissue.