The hardware-software system of differential diagnosis and evaluation of the efficacy of treatment of a number of extrapyramidal diseases (Parkinson's disease, essential tremor, idiopathic cervical dystonia) is based on the methodology of special processing of the electrical activity of muscles (EMG). The system defines the diagnosis for each investigated muscle, and determine various forms of extrapyramidal diseases including early preclinical ones. The system allows viewing the dynamics of changes in the patient's state, both in numerical characteristics and in the graphic interpretation, and evaluates the efficacy of various forms of treatment (medicament, surgical, etc.).