The methods based on the Group Contribution Concept usually fail when one attempts to estimate the physico-chemical properties of different branched isomers of a given compound. We present a new concept, the Group-Interaction Contribution Approach (GIG) which considers the contribution of the different interactions between groups present in a molecule instead of the contribution of structural groups.This approach allows differentiation between branched isomers, thus leading to different values of the physico-chemical properties. The GIC Approach can be easily implemented in current correlations based on the group contribution concept.The estimates of enthalpy of formation, normal boiling temperature and critical temperature of a series of 51 saturated hydrocarbons showed clearly that the GIC concept leads to very good estimations for branched isomers.