The recent theory of an equation of state of a fluid mixture is improved by generalizing the master equation form and analyzing the dependence of the exclusion factor on the mixture composition and cluster size. The formulas for computing the limiting value of the exclusion factor for a rarefied gaseous state and other parameters of an equation of state are derived for a multicomponent system. The previous variant of the theory is shown to be applicable to mixtures with the particle size ratios not exceeding 2. The theory presented in this paper has no restriction concerning the particle size ratios in a multicomponent system. The equation of state obtained is also reformulated in terms of reduced density. (C) 2003 American Institute of Physics.