Densities have been measured as a function of composition for a ternary-pseudobinary mixture of {(styrene+ethyl acetate or benzene) + (N,N-dimethylformamide + ethyl acetate or benzene)} by means of a vibrating-tube densimeter at atmospheric pressure and the temperature 298.15 K. The excess molar volumes V-m(E) were calculated from the densities and correlated using the Redlich-Kister equation to estimate the coefficients and standard errors. The experimental and calculated quantities are used to discuss the mixing behaviour of the components. The results show the third component, ethyl acetate or benzene, have a significant influence on the interaction between styrene and N,N-dimethylformamide. 0 2007 Elsevier Ltd. All rights reserved.