The aim of the work was to study in patients with delirium tremens (DT) in the acute period of the disease during the manifestation of hallucinations of the composition of the cerebrospinal fluid (CSF) — the clinical parameters of the CSF, the concentration of creatinine and urea in the CSF, as well as the content of non-ionic osmotically active substances in it. The study included 518 men in the acute period of DT. The age of the patients ranged from 20 to 75 years. The patients had both manifestations of “classic” DT (diagnosis code according to ICD-10 F10.4) and signs of different variants of severe DT (F10.43). All patients had manifestations of hallucinatory syndrome. According to the severity of hallucinatory disorders, 2 groups of observations were formed from patients with DT. Group 1: moderately pronounced hallucinatory syndrome (63 people). This group included patients with DT, in which manifestations of hallucinations were manifested both during direct examination and from their reports. There were short periods of visual hallucinations, in some cases in combination with auditory hallucinations; at the same time, a critical attitude towards them was sometimes partially preserved. Group 2: significantly pronounced hallucinatory syndrome (455 people). In patients of this group, hallucinatory disorders were detected during direct examination, there were long periods of pronounced visual hallucinations, often in combination with tactile, olfactory or auditory hallucinations; criticism of the experienced sensations was completely lost. In patients with DT with a significant severity of the hallucinatory syndrome, characteristic changes in the composition of the CSF were found: a relative increase in cytosis by 24 %, a moderate increase in total protein, as well as concentrations of urea and creatinine. The level of glucose in the CSF did not depend on the severity of hallucinations. A relative increase in the level of non-ionic osmotically active substances in the CSF was noted with a significant severity of the hallucinatory syndrome. Changes in the cellular and biochemical composition of the CSF in patients with DT with a significant severity of the hallucinatory syndrome may reflect a restructuring of the water-osmotic state in the cranial cavity with the development of cerebral edema.