Composite Group Vector Space (CGVS) method for estimating critical properties T-c, P-c, V-c of organic compounds has been proposed and principle of this method has been elucidated. Expressions for estimating T-c, P-c, V-c have been established with numerical values of relative parameters obtained. The average percent deviations of T-c, P-c, V-c estimation are 0.67, 2.09 and 1.39, respectively, which show that present method demonstrates significant improvement in applicability to predict the above properties, compared the conventional group methods. (c) 2005 Elsevier B.V. All rights reserved.