Other documents describe standard file formats for the distribution of luminaire photometric and component data. There is also a need to distribute spectral data. Such data are pertinent, but not limited, to the spectral radiant flux of light sources, the spectral transmittance of color filters, and the spectral reflectance of paint and other finishes. These data may be obtained when testing a light source, luminaire, or material and may then be used in lighting application software, rendering software, analysis software, or optical design software. This document specifies an electronic (XML based) data format for the transfer of spectral data. This document may be used for the transfer of spectral data of optical radiation including light sources, lamps, and luminaires, as well as reflectance and transmittance spectra of materials. The document is limited to containing a single spectral data set.