A comparison is made of a number of computationally efficient molecular ind
ices with a view to the screening of very large virtual data sets of molecu
les. The use of Bayesian regularized neural networks is discussed, and thei
r virtue in eliminating the need for validation sets, and potentially even
test sets, is emphasized. The concept: of a virtual receptor is introduced,
and this is illustrated by the results of screening a database of 40 000 m
olecules.