Abstract
It is the author's opinion that 500 r is the maximal safe total dose of ionizing radiation (half-value layer of 1.0 to 2.0 mm. of aluminum) in fractional doses at weekly intervals that should be given to the skin in treatment of a benign dermatosis; moreover, soft irradiation (grenz rays) will produce as good results in many dermatoses as standard superficial x-rays, with less risk of late sequelae. If a sharp and persistent erythema is produced by any single exposure, x-ray atrophy is almost certain to follow, even though it may be delayed for years. X-ray atrophy of the skin following treatment of a benign dermatosis is the most completely preventable of all serious human diseases.