A 30-fold increase in excretion of L-DOPA, distinct elevation in synthesis of dopamine and noradrenaline as well as inhibition of adrenaline synthesis occurred in schizophrenic patients at an acute period after administration of 0.1 g of L-DOPA per os (L-DOPA test). As shown by the L-DOPA test, excretion of L-DOPA was distinctly decreased in the patients with the remittence step as compared with the acute period. At the same time, in the remission synthesis of dopamine occurred mainly in the night time, synthesis of noradrenaline was decreased as compared with the acute period. synthesis of dopamine was increased 8-fold both in the patients at the acute period (mainly in the day-time) and within the remittence period (in the night-time) of the disease. The variations in excretion of L-DOPA, dopamine and noradrenaline, found in schizophrenic patients, were markedly distinct from dynamics of these patterns in healthy adult persons but were more similar to the parameters characteristic for persons in old and senile age. The L-DOPA test developed might be used for diagnosis of schizophrenia and of its periods (acute period and remission).