Communicative hydrocephalus (CH) is considered as one of the late sequelae of severe craniocerebral injury. However, as most of the series of patients with CH described in the literature deal with the results of various shunting procedures, the incidence of post-traumatic communicative hydrocephalus is not documented. We have found that almost 3-9% of 335 severe craniocerebral-injured patients develop communicative hydrocephalus. These patients were unconscious for various periods of time, therefore the triad described by Hakim and Adams cannot by itself lead the clinician to suspect possible development of communicative hydrocephalus. It is suggested that in prolonged coma, or in the presence of arrest in clinical progress in conscious craniocerebral-injured patients, communicative hydrocephalus should be suspected.