The effect of oxyphenbuhzorne (Tandearil) on the seromucoid proteila and seromucoid-bound carbohydrates of Walker 256 carci~lon~a bearing rats has beer1 investigated. InitiaHy, treatment is associated with increased tumor growth and slappression of the anticipated glycoprotein response in the serum. After the eighth day, tumor growth ceases in treated animals and the serum glycoproteins manifest progressive elevations which are, however, less than those observed in untreated tumor-bearing controls. The survival time of treated animals exceeded that of untreated tramor-bearing animals, and treated animals were free of gross malignant disease a t the time of death.Studies from anany laboratories have amply confirmed the elevation. of plasma or serum glycoproteins that accompanies malignant disease in the human (1-5) and in the laboratory animal bearing a transplantable tumor (6-10). Available evidence would suggest that the observed elevation occurs largely, if not exclusively, in the seromucoid fraction of the plasma proteins (8,9). This fraction, which is not precipitable by boiling a t slightly acid pH, is defined as a group of protein-carbohydrate complexes occurring in plasma that are soluble in 0.6 M prchloric acid but insoluble in 1 1ll phosphotungstic acid (11).Recent investigations have focused on a search for the source of the elevated plasma glycoproteins observed in malignant disease and a wide variety of acute and chronic inflammatory states. I t appears clear that in the normal anirnlal the protein binding of carbohydrates and synthesis of glycoproteins occur in the