Patients with chronic hydrocephalus are most often aged people and in bad general condition. It seems that treatment may be more simplest possible and the less iatrogenic. Furthermore, the diagnosis of chronic hydrocephalus is not often certain, and can be generally assert after the good result of the CSF shunting. Since 1985, when hydrocephalus appears communicant, a lumboperitoneal shunt was systematically implanted in the aim to decrease the number of complications due to ventricular shunts. The operation can be performed on neuroloptanalgesia and/or local anesthesia. Post-operative orthostatic intracranial hypotension can be prevented by using valves with opening pressure varying with the position or valves with a flow depending of the opening pressure. Our clinical series includes 82 patients (51 males and 31 females), aged from 27 to 88 years (average 55 years). In 47 cases, hydrocephalus was idiopathic and in 35 cases hydrocephalus was secondary to an identified aetiology: subarachnoid or intracranial hemorrhage (20 cases), post-traumatic (11 cases), post meningitic (1 case) and post anoxic (1 case). In this last case, physiopathological mechanism was unclear. The middle delay between the first symptom and the operation was greater than 6 months for the majority of observations, but in few cases, precoce shunting was performed (between 1 to 3 months) in post S.A.H. and post traumatic hydrocephalus when C.T. Scan shows increasing ventricular size. Clinical results are evaluated after 2 months and at long term, and complications analysed. The lumbo-peritoneal shunt gives same results on the clinical symptoms, and less iatrogenic complications than ventricular shunts.(ABSTRACT TRUNCATED AT 250 WORDS)