Effects of chicken egg white derivatives (EWD and EF-203) on the changes of blood cells and the neutrophil phagocytic activity were examined in the rats. Rats were administered orally with either EWD (200 mg/kg) or EF-203 (200 mg/kg) for 3 days. Thereafter, the changes of blood cell values (RBC, WBC, platelets, PCV, differential count of neutrophils) and the phagocytic activity of neutrophils were evaluated for 7 days. The numbers of WBC and the differential count of neutrophils of rats administered with either EWD or EF-203 were significantly increased (p<O.05 to 0.01) when compared to those of control rats receiving saline alone. In additional the phagocytic activity of neutrophils was remarkably augmented (p<0.01) by administration of either EWD or EF-203, suggesting that these egg white derivatives have an immunostimulating potent. And the numbers of platelets were also remarkably enhanced (p<0.01) by administration of either EWD or EF- 203, indicating that these substances also have a stimulating effect of platelets. However, there was no change in the values of RBC and PCV regardless of administration of either EWD or EF-203. These results suggested that chicken egg white derivatives including EWD and EF-2(13 induce the increase of platelets and the enhancement of nonspecific immunity on neutrophils.