3D-QSAR based on molecular interaction potentials is a technique with a long pedigree. However, current techniques have a number of issues which make it difficult to reliably produce effective models. Here we explain how QSAR using molecular field sampling has important advantages over grid-based sampling methods. No parameterization of grid size or spacing needs to be performed, the method is gauge invariant and reproducible, and edge effect are reduced as the sample positions are placed at the most important regions of space by construction. New software implementing this technique, ‘Forge’, is now available from Cresset.