Epileptic patients were examined for the daily urine elimination of DOPA, dopamine (DA), noradrenaline (NA), and adrenaline (A). The changes in the excretion of these substances after L-DOPA intake and the adrenaline and insulin test were also investigated. In addition to the evidence about the preserved reactivity of the DOPA-DA-NA-A system to L-DOPA intake, data were obtained pointing to its strain and a reduction in the reserve potentialities. The use of the adrenaline test disclosed the absence of, or a negative response on the part of DA and A in half of the patients, which correlated with definite clinical parameters. In one third of the patients, the insulin test was not accompanied by any increase in the excretion of A or its precursors. The findings obtained are indicative of the insufficiency of homeostatic reactions in epileptics and, possibly, of the deficit of the repolarizing mechanisms.