We studied the application of the diffuse reflectance spectrophotometry technique in order to obtain consistent hair-luster measurements. The influence on data quality of such experimental conditions as sample color, texture, geometry, and position, and of such instrumental operating conditions as viewing angle, viewing aperture, and inclusion or exclusion of the specular component, were established. The color-difference parameter (DE) appears as the best parameter to measure hair luster in CIELAB and FMCII systems of equations. Hair tresses submitted to several treatments, including shampooing and conditioning, were used to choose the best reference (zero-luster value) and hair-luster saturation (maximum-luster value). A luster scale was assembled from DE values, pointing out that diffuse reflectance spectrophotometry data allows measuring and quantifying hair luster.515289302