Development of compositional reservoir simulators is presently hampered due to the complexity of the existing computational algorithms of reservoir fluid phase behavior calculations. Through the application of the theory of polydisperse fluid mixtures we have developed a new algorithm for reservoir fluid phase behavior calculations. In this algorithm a reservoir fluid is considered to consist of a continuous mixture with a defined molecular weight/composition distribution. The proposed algorithm requires less computational time than the time required by the existing pseudocomponent VLE calculation methods. It is also shown that the new algorithm is applicable to varieties of equations of state and mixing rules. Results of the proposed technique are compared with results of the other existing techniques, and with the simulated multi-pseudocomponent reservoir fluid mixture data.