Recent results show that cresyl violet is useful, not only for histological staining, but also for visualization of nucleic acids on polyacrylamide gels. Furthermore, cresyl violet distinguishes between single-stranded RNA and DNA by producing red/magenta and blue bands, respectively. In order to develop a better understanding of these color differences, we are using visible spectrophotometry to study the dye/nucleic acid interaction in solution. The spectra reveal that the color changes are not simply due to wavelength shifts, but rather, to variations in wavelengths, absorbance maxima, and peak widths. Lineshape analyses are being used to characterize these variations, and to provide insight into the nature of the dye/nucleic acid interaction.