In this study, a new spectrophotometric method was developed for the determination of some textile dyes with different types of overlapping spectra. The binary mixtures of five dyes with yellow, scarlet, red, blue, and navy blue colors were analyzed by zero-crossing-point first-derivative spectrophotometry. The absorption spectra of the mixtures prepared in different ratios were recorded between 400 and 700 nm. First derivative amplitudes at appropriate zero-crossing wavelengths were selected for the determination of dyes in the mixtures. The proposed method was successfully applied to the determination of dyes with overlapping spectra in their bicomponent mixtures. The proposed derivative method is simple, rapid, and suitable for quantitative analysis of bicomponent dye solutions. (c) 2008 Wiley Periodicals, Inc.