BECAUSE of the rare occurrence of conversion of chronic lymphocytic leukemia to Hodgkin's disease, the following case is being reported. REPORT OF CASE G. P., a 67-year-old Swedish-born white man, was well until September, 1946, when he noticed a painless, nontender mass in the left side of the abdomen which began to increase slowly in size. Associated with the mass, he had a feeling of fulness after meals. Although his appetite was good, he lost 10 lb. (4.5 kg.) in weight during the following year. Because of these symptoms, he was admitted for study during September, 1947, to the Tompkins County Memorial Hospital, Ithaca, N. Y. Physical examination revealed no abnormality except enlargement of the spleen to below the umbilicus. Laboratory tests indicated a normal urine, a hemoglobin concentration of 11.8 gm. per 100 cc., and 4,590,000 erythrocytes and 4,600 leucocytes per cubic millimeter, with a differential count of 33%