Summary 1.There is no way of making a diagnosis of poliomyelitis in the absence of involvement of the central nervous system. In an attempt to determine its possible prophylactic and therapeutic value in clinical poliomyelitis, neoprontosil was given to 440 acutely ill children, during an epidemic of poliomyelitis, in approximate dosage of 1 grain per pound of body weight per day. A.Of these children, only one developed paralysis. This was a transient paralysis developing on the fifth day of illness in a child whose mother had not kept up the maintenance dose of the drug. Symptoms subsided when full dosage was resumed, and paralytic involvement had completely subsided in the three-week period of quarantine. B.Two other children developed meningeal symptoms on the fifth day of illness, under similar circumstances (noncontinuance of the maintenance dose). These symptoms subsided without paralysis with resumption of full dosage of the drug. 2. A.Fourteen cases of poliomyelitis are reported in which neoprontosil was given in the preparalytic stage. Of these, only one, the patient referred to above, developed paralysis. In this child the maintenance dose was not kept up, and the involvement, occurring on the fifth day of illness, was transitory (less than three weeks). B.Eight cases in which a clinical diagnosis of meningeal involvement of poliomyelitis was made subsided with neoprontosil medication without paralysis. They were not reported as positive cases because they were not confirmed by spinal fluid examination. 3.Eleven patients with paralytic involvement were treated during this time by administration of neoprontosil as above. Toxic symptoms subsided in this group within twenty-four to forty-eight hours, and there was no apparent advance in paralytic involvement after the adequate dosage of the drug was reached and held for twenty-four to forty-eight hours. There were no deaths in the acute phase of the disease. However, there were included in this series two acute fulminating cases with practically complete involvement of all extremities and respiratory musculature, necessitating the use of the respirator. One of these patients died two months later, while convalescing and recovering some respiratory function. Death was caused apparently by an attack of asthma, from which she had suffered for several years. Summary 1.There is no way of making a diagnosis of poliomyelitis in the absence of involvement of the central nervous system. In an attempt to determine its possible prophylactic and therapeutic value in clinical poliomyelitis, neoprontosil was given to 440 acutely ill children, during an epidemic of poliomyelitis, in approximate dosage of 1 grain per pound of body weight per day. A.Of these children, only one developed paralysis. This was a transient paralysis developing on the fifth day of illness in a child whose mother had not kept up the maintenance dose of the drug. Symptoms subsided when full dosage was resumed, and paralytic involvement had completely subsided in the three-week period of quarantine. B.Two other children developed meningeal symptoms on the fifth day of illness, under similar circumstances (noncontinuance of the maintenance dose). These symptoms subsided without paralysis with resumption of full dosage of the drug. 2. A.Fourteen cases of poliomyelitis are reported in which neoprontosil was given in the preparalytic stage. Of these, only one, the patient referred to above, developed paralysis. In this child the maintenance dose was not kept up, and the involvement, occurring on the fifth day of illness, was transitory (less than three weeks). B.Eight cases in which a clinical diagnosis of meningeal involvement of poliomyelitis was made subsided with neoprontosil medication without paralysis. They were not reported as positive cases because they were not confirmed by spinal fluid examination. 3.Eleven patients with paralytic involvement were treated during this time by administration of neoprontosil as above. Toxic symptoms subsided in this group within twenty-four to forty-eight hours, and there was no apparent advance in paralytic involvement after the adequate dosage of the drug was reached and held for twenty-four to forty-eight hours. There were no deaths in the acute phase of the disease. However, there were included in this series two acute fulminating cases with practically complete involvement of all extremities and respiratory musculature, necessitating the use of the respirator. One of these patients died two months later, while convalescing and recovering some respiratory function. Death was caused apparently by an attack of asthma, from which she had suffered for several years.