Room temperature ionic liquids are receiving growing attentions as green solvents for reactions and separations. In particular, ionic liquids + carbon dioxide systems are of importance in the recovery of solutes in supercritical fluid extraction. Solubilities of carbon dioxide in ionic liquids, [bmim][PF6], [C(6)mim][PF6], [emim][BF4], [C(6)mim][BF4], [emim][Tf2N] and [C(6)mim][Tf2N], were experimentally studied at 298.15 K and up to 1 MPa in the present study. Present and literature data were fitted to determine group segment numbers and interaction energy parameters between groups for the group contribution non-random lattice-fluid equation of state. The agreements between data and calculated solubilities and densities were found generally good for ionic liquids with 1-alkyl-3-methylimidazolium cations and [PF6], [BF4] and [Tf2N] anions. (c) 2004 Elsevier B.V. All rights reserved.