As our clinical investigations relating to uptake of radioactive phosphorus (P32) by neoplastic and inflammatory lesions within the eye have proceeded during the past few years, it has become increasingly desirable to build a firmer foundation for these empirical clinical observations by means of controlled experiments in animals. In planning these experiments, the principal purpose has been to elucidate the clinical observations and to evaluate more accurately the various technical factors which enter into these determinations. Our investigations have been based on a large body of work and knowledge already gained by others on the uptake of radioactive material, particularly radioactive phosphorus, by various types of malignant tissue and on the facts that have been learned about the metabolism of phosphorus in normal and malignant cells. In addition, we could avail ourselves of a tested method of producing tumors in the eye, i. e., the technique of transplantation of