We have studied the dyeing kinetics of acrylic fibers containing hydrolyzed acry lonitrile terpolymer ( varying degrees of hydrolysis), secondary cellulose acetate, poly vinyl pyrrolidone, glycerol, and polyvinyl acetate as spinning dope additives (5% on weight of terpolymer) using basic dyes. Diffusion coefficients for the dyes are calculated from Crank's equation and related to the molecular sizes of the dyes as well as the structure of the blend fibers. The dye uptake values are enhanced by spinning dope additives, the extent being greater in the fibers containing hydrolyzed acrylonitrile terpolymer, secondary cellulose acetate, and polyvinyl pyrrolidone as the additives. We attribute this to loose packing of polymeric chains, low glass transition temperature, more amorphous content, less x-ray orientation, and lower activation energy of these fibers. We also studied the light- and washfastness of the dyed fibers.