The uncertainty surrounding the background of both mycosis fungoides and Kaposi's sarcoma lends an added interest to the coincidental occurrence of the clinical manifestations of the two diseases in the same person. Mycosis fungoides developed first in a patient who came under our observation, and later a blood picture characteristic of a mild lymphatic leukemia appeared. In the last four months of his life a mass of nodules developed on the right foot with a few lesions elsewhere, having the histologic characteristics of Kaposi's sarcoma. Many authorities have grouped mycosis fungoides, the leukemias, Hodgkin's disease and lymphomas under the general term lymphoblastoma. This lymphoblastoma group as a whole has many puzzling features, and every unusual case in this group, while it may complicate the picture at present, may contribute with the summation of evidence to the clarification of the relationships within the group. REPORT OF A CASE