As changes of content of aminoacid and their derivates are one of the reasons of origin of pathological processes, which are related to dysfunctions of the nervous system, the deep study of this link of metabolism at Parkinson’s disease is expedient. It was conducted the determination of content of the complex of aminoacid in blood serum of the patients with Parkinson’s disease with the different degree of severity. The exposed diff erences in the dynamics of changes of levels of neuroactive aminoacid testifi es that at the progressing of Parkinson’s disease there is not only the phenomenon of "XI-toxicity", but it is also marked the forming of the disbalance between the excitant and inhibitor mechanisms with the signs of insuffi ciency of the protective braking, that determines the severity of the disease. Some displays of Parkinson’s disease can be related to the neurotoxic action of excitant neuromediative aminoacid and hypoactivity of inhibitory, and also with the changes of the balance of lysine and homocystein.