Abstract. At the modern stage in Russia, we can observe the tendency of increase in recording cases of neurosyphilis against the background of reduction of morbidity rate of syphilitic infection in general. Increase of neurosyphilis morbidity reflects the situation of frequency increase of primary forms of syphilis in the end of the 90s – beginning of the 2000s, when our country faced with epidemic of this disease. Most experts assume that treponema pallidum always penetrates in the nervous system, in some cases its presence being transitory, in other cases, we observe asymptomatic persistence, and in some, neurosyphilis manifests. Currently, most often syphilis therapy takes place on outpatient basis with repository forms ((Benzathine benzylpenicillins) which create long (during several days and up to 18-21 days after one-time administration), but low concentration of penicillin in the body. These drugs badly overcome blood-brain barrier, consequently, if syphilitic meningitis is latent and not diagnosed, liquor sanation is not achieved, and potential development of neurosyphilis manifest forms is retained. The authors describe the difficulties of diagnosis of neurosyphilis and a clinical case of ischemic stroke in a young patient with neurosyphilis. Diagnosis of syphilis was confirmed by laboratory studies; liquor tests and clinical data allowed to diagnose meningovascular syphilis. The authors highlight that special attention should be paid to observance of algorithm of clinical-laboratory examination of patients if they have disorders in functions of central and peripheral nervous systems, organs of vision and hearing, regardless of remoteness of supposed infection and supposed seroresistance. As neurosyphilis is interdisciplinary problem, complex clinical-laboratory and clinical-instrumental examination of patients is required, involving medical specialists of different profiles. For citation: Vizilo T. L., Poponnikova T. V., Fedoseeva I. F., Vasenina E. D. The difficulties of diagnosis of neurosyphilis at the modern stage // Lechaschi Vrach. 2021; 10 (24): 28-34. DOI: 10.51793/OS.2021.24.10.005