• Urea in amounts as high as 1 gm. per kilogram of body weight can be injected intravenously in the form of sterile, fresh 30% solution in 5% dextrose. Urea was used without causing toxic reactions in 21 patients. The desired reduction in cerebrospinal fluid pressure was accomplished in every case. There was no secondary rise such as is seen after injections of hypertonic solutions of sodium chloride and dextrose, and the blood pressure was unaffected. Heat must not be used to sterilize the urea solution. If the technique is carefully followed, it should be valuable in brain surgery for the reduction of intracranial pressure.