A diffuse involvement of the meninges by carcinoma is described in three cases characterizing the so called "meningeal carcinomatosis". The neurologic symptoms were those of the chronic meningitis or encephalomyelitis, with changes in the spinal fluid. The morphologic features were identical in the three cases and represented by slight to moderate thickening of the meninges by diffuse infiltration of tumor cells and few foci of inflamatory reaction. The cases 1 and 3 were represented by well differentiated adenocarcinoma with primary site in the lung and gallbladder, respectively. In case 2 the tumor was a poorly differentiated carcinoma of stomach with diffuse involvement of the arachnoid and dura mater associated with recent hemorrhage. An interesting point was the lack of correlation between clinical and pathological findings. The clinical symptoms were very prominent and the gross findings only slight to moderate. The criteria for diagnosis of this entity as well as the mechanism of dissemination of the carcinoma to the meninges are reviewed and discussed.