Antibodies were isolated from the yolks of hens that were immunized with a variety of plant viruses by the use of polyethylene glycol (PEG). A concentration of 3.5% of the polymer caused the lipids and vitellin to separate, and the IgY was then precipitated with 12% PEG. The titre of the isolated antibody appears to remain at a high level after cessation of the course of immunization. Antibodies derived from the yolks of hens appear to have titres similar to those found in serum of rabbits immunized simultaneously. The observation made by several authors that a high salt concentration enhances fowl serum antibody precipitin titres could not be corroborated with 'yolk' antibodies directed against several plant viruses.