Summary 1. From June, 1944, through December, 1949, there were admitted to the Geisinger Memorial Hospital 320 cases of acute anterior poliomyelitis. Forty-three or 13.8 per cent of the patients showed no abnormal findings in the spinal fluid although they had the characteristic signs and symptoms of the disease. Five of the patients were nonparalytic at the time of discharge while the other 38 patients showed slight to severe paralysis. At the end of a three months' follow-up, 51.1 per cent had completely recovered, 34.9 per cent had residual weakness, and 14 per cent had severe paralysis. 2. It was observed that 32.6 per cent of these patients had the spinal tap done on the first day of the disease and 74.6 per cent within the first four days. 3. The diagnostic criteria for paralytic and nonparalytic poliomyelitis as formulated by the National Conference on Recommended Practices is the best outline to follow in the diagnosis of this disease at the present time. 4. The diagnosis of acute poliomyelitis should be made from the clinical observations with the aid of the spinal fluid findings by a physician qualified by experience and training to make such a diagnosis.