THE AIM of the study is to describe clinical observations of patients with central nervous system lesions of infectious etiology and to analyze the tactics of examination and differential diagnosis with brain diseases requiring surgical treatment. MATERIALS AND METHODS. There are two clinical observations of patients hospitalized for emergency indications at the St. Petersburg State Budgetary Healthcare Institution “City Mariinsky Hospital” presented. Ом of them - with suspected closed craniocerebral trauma (CCI), the other - with acute cerebrovascular accident (ACVI) of the ischemic type and occlusive hydrocephalus in the stage of subcompensation. As a result of the examination, in the first case, toxoplasmosis of the brain was diagnosed against the background of HIV infection in the AIDS stage, in the second - tuberculous meningoencephalitis. RESULTS. The carried out diagnostic measures made it possible to make an accurate diagnosis in time and plan the treatment of patients correctly.