gray hair as has been reported in human beings (32, 37, and 38). In the Japanese bomb casu- alties (30) and the Japanese fishermen (11) the regrown hair was also normal in color, texture, and abundance. The nature of the bluish-brown transverse bands of pigmentation that developed beneath the nails is not known. Since it occurred in the majority of the more heavily exposed Mar- shallese groups and in all five of the American Negroes, but none of the white Americans, it appeared to be a response peculiar to dark~skinned races. The phenomenon was apparently produced by whole-body radiation with dosage as low as 75 r since this was the estimated dose the American Negroes received in the absence of significant contamination of the hands. Sutton (39) has reported a case of similar fingernail pigmentation which developed in a negress, follow ing 150 r of soft X-irradiation to the hands. Certain conclusions may be drawn from this experience concerning the hazard of radioactive fallout in regard to the skin. (1) Serious contamination of personnel with fallout may occur many miles from the site of detonation of a nuclear device; (2) Beta radiation of the skin may result in extensive epilation and skin lesions even though the dose of whole-body penetrating radiation received may be sublethal; (3) Just as the dose of whole—body radiation can be decreased by early evacuation so can skin irradiation be reduced by prompt personnel decontamination. One can conceive of a situation following fallout where early evacuation from a field of radiation mght result in a minimal whole-body dose of radiation, but due to delayed decontamination of the skin. for various reasons, serious skin exposure might occur. The re- verse situation might occur if decontamination were possible early, but evacuations were de- layed and adequate shelter against penetrating radiation were not available; of prompt decontamination cannot be overemphasized. (4) The importance The earlier the fallout occurs the more radioactive is the material and the higher the dose rate. Therefore, prompt decontamination is exceedingly important when fallout occurs within several hours after the detonation. Diffi- culty encountered in decontamination of the hair may necessitate cutting off the hair or shaving the head if contamination is great; (5) Warm weather would tend to aggravate the hazard since increased perspiration would tend to concentrate the material and cause it to stick, and less clothing would increase exposure and; (6) Simple preventive measures may completely eliminate or greatly reduce the hazard of skin irradiation. Recognition of the powdery, ash-like material as radioactive fallout should not be difficult. Preventive measures center around avoidance of the deposit of fallout on the skin. Taking shelter or keeping indoors during the fallout are obvious safety measures and covering as much of the body as possible with clothing, even a single layer, will provide marked protection. SUMMARY Radioactive fallout from an experimental thermonuclear detmation resulted in accidental exposure of 239 Marshallese people, and 28 American servicemen. Whole-body exposure to penetrating radiation, beta radiation of the skin, and a small amount of internal absorption of radioactive materials occurred. Beta lesions of the skin, epilation and nail pigmentation are described. This report covers the results of examinations immediately after the accident, again at 6 months and at | year after the accident. During the first 24 to 48 hours, itching and burning sensations of the skin occurred lasting only a, day or two. Lesions began developing 2 and 3 weeks later on exposed parts of the body in roughly the following order: scalp with epilation, neck, axillae, antecubital fossae, feet, limbs and trunk. No primary or secondary ery- thema was observed. The majority of lesions were superficial and occurred in about 90 percent of the higher exposure groups. They were characterized by pigmentation which was accompanied by mild itching and burning sensations of the skin, followed by dry desquamation leaving de- pigmented areas which gradually repignented to normal color. Some 20 percent of the lesions in the highest exposure group were deeper and were characterized by pain, wet desquamation and ulceration. Some of these deeper lesions showed persisting aberrations in pigmentation and some degree of atrophy. There has been no breakdown of the skin noted in any lesions after 438