The phase equilibrium of the binary system N,N-dimethylacrylamide (DMAAM)-CO2 and the influence of the presence of dyes Cl Disperse Blue 79 and Cl Disperse Red 60 on the DMAAM-CO2 System have been investigated. The behavior of the binary system CO2-DMAAm was determined through the measurement of the bubble/dew points at different temperatures for several mixture compositions. The experimental data of the binary system CO2-DMAAm were modeled by using the Peng-Robinson equation of state. The critical properties and the acentric factor of DMAAm were calculated by using group contribution methods. The bubble point of the ternary system CO2-DMAAm-disperse dye overlaps the curve of the CO2-DMAAm binary system at the levels studied. The measured equilibrium data were used to interpret the dyeing results of films and knitted fabrics of PET modified with DMAAm and knitted fabrics of PET modified with ultraviolet (UV)/DMAAm in supercrtical CO2. We observed that the determination of the phase diagram for the CO2-DMAAm system is important for choosing the best dyeing region of DMAAm-and UV/DMAAm-modified PET films and knitted fabrics in supercritical CO2. (c) 2006 Elsevier B.V. All rights reserved.