We describe the use of Bayesian regularized artificial neural networks (BRA
NNs) coupled, with automatic relevance determination (ARD) in the developme
nt of quantitative structure-activity relationship (QSAR) models. These BRA
NN-ARD networks have the potential to solve a number of problems which,aris
e in QSAR modeling such as the following: choice of model; robustness of mo
del; choice of validation set; size of validation effort; and optimization
of network architecture. The ARD method ensures that irrelevant or highly c
orrelated indices used in the modeling are neglected as well as showing whi
ch are the most important variables in modeling the activity data. The appl
ication of the methods to QSAR of compounds active at the benzodiazepine an
d muscarinic receptors as well as some, toxicological data of the effect of
substituted benzenes on Tetetrahymena pyriformis is illustrated.