1. A large daily dose of sodium carboxymethylcellulose was given to a group of patients for a six month period. 2. Careful study of the effect on the blood cell constituents was made. 3. No significant effect on the blood cell constituents could be ascertained as resulting from the administration of sodium carboxymethylcellulose. Bone marrow was also unaltered in a small group of patients in which such study was done. 4. Many of the patients tolerated much larger doses than are ordinarily used therapeutically without ill effect.