A high pressure, xenon arc, grating monochromator was used to study the erythema action spectrum in 36 subjects in the spectral region 250 mμ to 310 mμ. The resultant erythema action spectrum is characterized by continuously decreasing efficiency from a maximum at 250 mμ. A second maximum at 297 mμ and a minimum at 280 mμ as reported by others was not observed and is believed to be an artifact of method.