A new 3-parameter attraction term for the Soave-Redlich-Kwong equation of state, that ensures a correct physical behaviour, is proposed to improve its predictive capabilities, particularly in the supercritical region and in the gas phase. Vapour pressure and second virial coefficient data for a set of eight pure fluids with a low acentric factor omega (Ar, Ne, Kr, O-2, N-2, C-H, CO and C-2-H-6) are used to determine the equation's adjustable parameters. When only vapour pressure data are considered the supercritical region is poorly described. An extension of the data base by including for instance the second virial coefficient data leads to a significant improvement in the description of the sub and supercritical regions of the considered fluids and particularly in the prediction of the Joule-Thomson inversion curves. The new attraction term is shown to be suitable for other pratical fluids like hydrocarbons as well as their mixtures.