The clinical and radiological findings in 18 patients suffering from arachnoid cysts of the middle fossa (ACMF) are reported. The importance of computed tomography in diagnosis and in the assessment of surgical therapy in 15 cases is emphasized. The indication to operate upon ACMF and criteria of adequate surgical treatment are discussed. We want to point out the superiority of simple shunting procedures over craniotomies and removal of membranes.