Some fish, including the guppy, have the ability to perceive ultraviolet (UV) wavelengths. Female guppies prefer to associate with males that are viewed under light conditions that include UV-A, in preference to conditions lacking these wavelengths. We used reflexion spectrophotometry to show that male guppies reflect UV light from both their structural (purple, green and white) and pigment (orange) colour patches and that males differ in the levels of UV light reflected. Varying components of UV may affect both the brightness and hue of particular colour patches. This may produce nonspectral colours that are visible to the guppy but that are outside human perception. We used video analysis to quantify male reflexion in the UV and visible wavebands. Male guppies with high and low UV reflexion, but similar human-visible coloration and area of coloration, were paired for use in mate choice experiments. Female guppies shown pairs of males differing in their levels of UV reflexion had no preference for either high or low UV reflexion. This suggests that UV reflexion does not provide particularly significant information relating to male quality or influence female preference in this population of guppies.