The recently proposed WHIM (Weighted Holistic Invariant Molecular) approach [Todeschini, R., Lasagni, M. and Marengo, E., J. Chemometrics, 8 (1994) 263] has been applied to molecular surfaces to derive new 3D theoretical descriptors, called MS-WHIM. To test their reliability, a 3D QSAR study has been performed on a series of steroids, comparing the MS-WHIM description to both the original WHIM indices and CoMFA fields. The analysis of the statistical models obtained shows that MS-WHIM descriptors provide meaningful quantitative structure-activity correlations. Thus, the results obtained agree well with those achieved using CoMFA fields. The concise number of indices, the ease of their calculation and their invariance to the coordinate system make MS-WHIM an attractive tool for 3D QSAR studies.