The case reported here is of a man, for many years a feather dyer, whose habit it was to test his dye solutions by tasting, who for some time preceding his death from coronary thrombosis showed a marked increase of red corpuscles. He had exhibited cyanosis long before the polycythemia was first noted (1919). During his last period in the hospital there came to visit him a young woman, Miss M. D., who, we discovered, had also suffered polycythemia (12,400,000 at one time), and whose improvement following irradiation and benzene treatment had been reported by Hurwitz and Falconer.1 She had given them (in 1915) her occupation as milliner, but further inquiry now (July, 1919) brought out the fact that she had in reality also engaged extensively in the dyeing of feathers, having been an active associate in the business with our patient from about 1912 to 1916. With this