The authors report on four cases of intra-ventricular lesions surgically treated by endoscopic laser-therapy in stereotactic conditions. Two colloid cysts of the third ventricle, one arachnoidal cyst responsible for with an intracranial hypertension and an intraventricular meningioma were treated with such a procedure. The laser beam was used as a surgical knife on cystic lesions and to vaporize the meningioma. The laser coupled with an endoscope add to the comfort given by direct visualization the precision of surgical instrument the effects of which are perfectly controllable in areas where surgical traumatism must be avoided as much as possible.