Abstract It is the purpose of this paper to outline the present state of art for determining K-factors, in particular those which apply to volatile oil and condensate fluids. Equations are presented that can be used to select K-factors for volatile fluids through convergence pressure calculations. These empirical pressure calculations. These empirical correlations can be used for calculating the K-factors for all the components in a mixture, at pressures greater than 0.7 times the convergence pressure. Relations are also presented to compute the K-factors of C+7 presented to compute the K-factors of C+7 fraction as a function of molecular weight, convergence pressure, and the operating pressure. Pressure-temperature phage envelopes pressure. Pressure-temperature phage envelopes are presented for four multicomponent hydrocarbon mixtures that were used in validating the proposed correlations in this paper. proposed correlations in this paper. The current limitation of the equation of state approach for calculating K-factors for volatile fluids is demonstrated through phase diagrams. Introduction The U. S. is currently faced with an energy shortage that has resulted in deep-well exploratory drilling (down to 28,000 ft). Reservoirs discovered at these greater depths are more likely to contain volatile fluids, since the reservoir pressure and temperature are higher than those presently being produced at more shallow depths. Due to the nature of these fluids, the ability to calculate reservoir performance and thus predict recoverable performance and thus predict recoverable reserves will, in part, require the accurate determination of their phase compositions and accurate predictions of the densities of the equilibrium phases. The phase composition calculation results in mass conservation, while an accurate phase-density calculation results in the conservation of pore volume. This paper is concerned with the former problem, the accurate determination of the phase compositions at various stages of reservoir depletion. In turn, the calculation of phase compositions requires accurate K-factors. These K-factors are particularly difficult to determine for volatile particularly difficult to determine for volatile reservoir fluids, especially near the critical state.