1. Aqueous extracts of Chicken Tumor I cause a disintegration of yeast nucleic acid.
2. Two enzyme activities, a polynucleotidase and a phosphatase, are demonstrated.
3. These activities are distinguished by different reactions to an environment of hydrogen, different optima of hydrogen ion concentration, and different rates of activity.
4. Adsorption with aluminum hydroxide Type C removes substances inhibiting the polynucleotidase activity.
5. There is a rough proportionality between the polynucleotidase activity and the tumor-inducing power of different fractions of extracts of Chicken Tumor I.
6. There is a rough proportionality between the inhibition of polynucleotidase activity and the inhibition of the tumor agent.
7. The polynucleotidase activity of Chicken Tumor I is as great as that of spleen, slightly less than that of kidney and liver, but much greater than that of muscle. There are also qualitative differences.