A method to build the Cubic Equation of State of a simple substance is presented. Inputs are critical compressibility, acentric factor and saturated vapor volume. Cubic Equation of State is unique for each substance. Abstract: A method to define the Cubic Equation of State (CES) of a simple substance is presented in this work. CES is constructed with only three parameters of the fluid, namely, the critical compressibility Z(c) = P(c)v(c)/RTc, the acentric factor omega -log (P-(sat)/P-c) - 1 (where P-(sat) is the saturated vapor pressure), and the saturated vapor volume v((sat)) at the temperature T-(sat)/T-c = 0.7 (where T-c is the critical temperature, v(c) is the critical volume, and P-c is the critical pressure). The resulting CES is unique for each substance and, in general, it is different from other known CES in the literature. (C) 2011 Published by Elsevier B.V.