The authors explain the clinical aspects presented by the arterial intracranial aneurisms. They base their classification in their own experience which is of 30 aneurisms and present 9 typical cases which they describe clinically and arteriographically, and the surgical method used. The diagnostic of the arterial aneurismas and its localization is always accurately obtained by the arteriography (the authors have made 400 arteriographies without a serious accident). They consider the classification that follows as previous and susceptible of being modified or enlarged according to experience: 1) form with meningeal hemorrhages; 2) form with paralysis of the extrinsic muscle of the eyes; 3) pseudo-tumoral form; 4) pseudo-encephalitic form; 5) form with epilepsy, clinically essential.