The incidence of cerebral toxoplasmosis (CT) among all brain involvements was determined in patients with Stage 4B HIV infection (AIDS) in 2003-2009. Clinical and laboratory parameters were estimated in 156 patients to reveal diagnostic criteria. As a result, CT was shown to be a leading cause of neurologic diseases in patients with late-stage HIV infection (34.7% of cases of brain involvement). In 11.5%, it took place as a generalized process. CT concurrent with cytomegalovirus infection, tuberculosis, or other secondary lesions was frequently diagnosed. Of importance in the diagnosis of CT are magnetic resonance imaging results in addition to basic, clinical data that can assume this diagnosis. The high and moderate serum concentrations of T.gondii IgG are of diagnostic value, which may be used as an auxiliary method to verify the diagnosis.