Major types of lymphoblastoma, that is, leukemia, Hodgkin's disease and lymphosarcoma, as well as mycosis fungoides, have been shown to merge into each other in the same person in numerous cases ( Keim,1 Fraser2 and Wile3). There are many instances of familial leukemia on record. Striking cases have been cited by J. Chalmers Cameron,4 Sanger5 and von Brügger.6 Hodgkin's disease has been well reviewed and studied, as regards its familial occurrence, by Arkin.7 He found cases reported in twins (Peacock and Senator), in a brother and sister (Degen) and in a woman and two brothers ( Braun). Arkin himself reported mediastinal Hodgkin's disease in a man, in his son and in his nephew. REPORT OF CASES I have been unable to find in the literature reports of two cases of mycosis fungoides in the same family. I believe that the following two cases are