Radiant energy of wavelengths shorter than 3200 1 was excluded by Pyrex glass in producing cutaneous bums in the pig with the carbon arc so\irce. The 50^ effective exposures for burns so produced were conrpared with those escposiires required with the caxbon axe source alone at 0.5 sec. exposxire times.It was found that excltision of the shorter ultraviolet wavelengths increased the 50?^ effective exposiire of radiation required to produce 1+, 2+, 3+ and k+ bums. Ultraviolet radiation had a most marked effect in producing erythema (l+ burn); the 5^5^ effective exposure was increased two-fold with its exclusion. No effect was observed in the 50^ effective exposxire for the threshold of complete transepidermal damage Judged by depth of damage microscopically produced with or without the short wavelength radiation.