The authors describe the technique and explain the reason for the use of an intravascular balloon catheter technique in the treatment of vasospasm in cases of subarachnoid haemorrhage due to rupture of a cerebral aneurysm. In 33 patients with SAH 105 major cerebral arteries were dilated (in the system of internal carotid and basilar arteries). Only in one case vasodilatation could not be accomplished. The effect of dilatation of vasospastic arteries was stable and the functional state of the brain was ameliorated, local and general cerebral dysfunctional signs and symptoms due to vasospasm regressed. The authors discuss indications and contraindications for intravascular balloon dilatation of spastic arteries, the time for the operation, the length of arteries to be dilated, and the possible mechanism of amelioration of cerebral blood flow to the brain stem.