Concentration of cyclic adenosine 3’,5’-monophosphate (cAMP) and activities of some enzymes were measured in cerebrospinal fluid (CSF) from 38 patients with various cerebrovascular diseases. Cerebral infarction of the carotid area <14 days after the attack) revealed a significant increase in CSF cAMP level in comparison to a transient ischemic attack (TIA) and cephalalgia without any pathological findings (control group). A trend towards elevated values was observed also in cerebral hemorrhage, whereas the CSF cAMP concentrations in subarachnoid hemorrhage, TIA, syncope, and cerebral infarction of at least 2 months of duration were in the range of control values. A significant rise in CSF enzyme activities was observed only in hemorrhagic disorders. Hypertensive patients with TIA showed significantly higher CSF cAMP values than normotensive ones. A similar positive correlation between blood pressure and CSF cAMP concentrations was found also in subarachnoid hemorrhage and syncope groups. On the basis of the present results it is suggested that in cerebrovascular diseases CSF cAMP concentration reflects the size and the time of the destruction of cerebral cells, and correlates with hypertension of the patient possibly indicating an increased sympathetic activ