Abstract: Hazy or frosty appearance of mixtures of polyester and cellulosic fibers when dyed with disperse dyes is suppressed by adding to the aqueous dye bath a small amount of low copolymer of acrylamide or the like with a water-soluble maleic or fumaric acid ester, and with or without an additional water-soluble vinyl compound, all as defined infra. The copolymer is normally a liquid miscible with water in all proportions at 10.degree. C. or below. Disperse dye is fixed to the polyester fibers by heating as in the Thermosol process. Dyes for the cellulosic fibers can also be included in the dye bath so that the cellulosic fibers are also dyed in the same treatment. Alternatively the cellulosic fibers can be separately dyed, preferably after the polyester fibers are dyed.