For compositional simulation purposes, a new method has been developed for estimating the specific gravities of pseudo-components that are required to characterize the heavy components of crude oils. This method makes use of the always available data for the heavy components of crude oils: average molecular weight and specific gravity of the heptanes-plus (C-7+) fraction. To evaluate the new method and compare it with the existing estimation methods, a procedure has been implemented for the phase equilibrium predictions of crude oil/carbon dioxide systems without using any tuning techniques. The phase equilibrium predictions, based on the specific gravities estimated by the new method and the existing methods proposed by Whitson et al. (1989) and Yarborough (1979), were all reasonably accurate and of the same magnitude. The specific gravities estimated by the new method and the method proposed by Whitson et al. (1989) always provided similar predictions. The satisfactory results reported here also indicate that a simple truncated exponential distribution for the heavy components of crude oils is adequate.