We appreciably broaden the scope of existing thermodynamic perturbation theory for pure fluids in several ways. Analytical approximation strategies are combined to express the thermodynamic properties of fluids in analytical and/or algebraic form and applied to a generalized class of pair potentials. The results are illustrated by comparing previously reported simulation measurements with our predictions obtained using a new class of generalized Lennard-Jones potential functions with independently adjustable repulsive and attractive length scales. Results are also obtained for various purely repulsive fluids, including inverse-power potentials with exponents ranging from 12 to 72 and a Lennard-Jones repulsive reference fluid. Applications to argon (Lennard-Jones) and C-60 (Girifalco potential) are used to probe the limits of applicability of first-order perturbation theory to systems with very short range attractive potentials. Furthermore, we discuss the role of these new results in a number of additional applications. (C) 2003 American Institute of Physics.