DFT calculations on over 60 hydrogen bond bases and their complexes with hydrogen fluoride have been performed. By using properties computed at the B3LYP/6-31 +G(d,p) level of theory as predictors of pK(HB) multivariate analysis, the hydrogen bond scale can be regarded as a composite descriptor made of an electrostatic term (by using the minimum value of the electrostatic potential on the 0.001 a.u. isodensity contour surface of the isolated base) and of an overlap term (by using the bond order or the energy density calculated at the bond critical point of the most stable 1:1 HF complex). (C) 2002 Elsevier Science B.V. All rights reserved.