Prior to the report of Stokes and Neefe1indicating the value of gamma globulin from pooled human plasma in the prevention and attenuation of infectious (epidemic) hepatitis, no method of control of outbreaks of this disease had been available. The extensive literature on infectious (epidemic) hepatitis that has accumulated in the past several years bears witness to the widespread occurrence of this disease both in the armed services and among civilian populations. The lengthy period of convalescence following infectious hepatitis has made it of prime importance to the armed services of all the United Nations. On the basis of the report of Stokes and Neefe and on the recommendation of the Surgeon General, U. S. Army, and at the invitation of the Chief Surgeon and the Commanding General, Mediterranean Theater of Operations, U. S. Army, to two of the authors of this present report, field studies on the effectiveness