We present results of vapor-liquid equilibrium and critical points calculated using the group-contribution version of an equation of state based on the generalized Van der Waals theory and combining the Staverman-Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression. Group parameters were fitted using pure component and mixture VLE data. Critical points were calculated using a modified form of the Hicks and Young algorithm. Results for pure components and mixtures were satisfactory in the correlation and prediction of several properties. In the case of critical points, several qualitative aspects of the critical curves in the systems tested could be predicted using this group-contribution EOS and were in agreement with experimental information available in the literature. Even though mixture calculations were limited to n-alkane systems, work is in progress towards the inclusion of additional groups needed to represent other compounds of interest in the oil industry.