Treatment of the important electrostatic effects of solvation by means of reaction field theory is becoming common in electronic structure calculations on molecules. Most extant reaction field methods neglect or crudely approximate the often important influence of volume polarization arising from solute charge that quantum mechanically penetrates outside the cavity that nominally encloses it. This work proposes and examines a new formulation that provides an accurate simulation of volume polarization effects while being much simpler to implement and use than an exact treatment. Detailed comparisons with other related methods are also given. (C) 2000 American Institute of Physics. [S0021-9606(00)30513-X].