Fluorescent whitening agents (FWAs) are chemicals added to most fabrics and papers during manufacture to increase color temperature, "whiteness," and "brightness." FWAs accomplish this by absorbing energy in the ultraviolet (UV) part of the spectrum and emitting it as visible blue light. Recently, hunters have become concerned that FWA could be reducing the effectiveness of their camouflage clothing. As a result, some manufacturers have begun making their camouflage clothing (camo) without FWA, and a spray-on product has been introduced to block the action of FWA. Radiometric spectra from camo and foliage samples suggest, however, that these concerns might not be fully justified. Under full sun and in the shade, spectra from 300 to 500 nanometers (nm) (i.e., UV and visible blue light) showed that camo samples containing FWA matched the foliage reasonably well. No evidence of a major problem caused by the FWA was detected, and no significant need for the use of UV absorbing dyes to block the action of FWA was found.