Spartan is the most sophisticated version offered. The latest Spartan release offers all features and methods included in the Spartan Essential Edition, and in collaboration with Q-Chem, provides a full range of post-Hartree-Fock methods including Density Functional, Moller Plesset, Thermochemistry recipes (including the new T1 procedure), and an assortment of Advanced Correlated approaches. Spartan'08 is the dominant version used in academic, government, and commercial research