Overview of quantitative drug design -- Noncovalent interactions in biological systems -- Preparation of 3D structures of molecules for 3D QSAR -- Calculating physical properties of molecules -- Biological data -- Form of equations that relate potency and physical properties -- Statistical basis of regression and partial least-squares analysis -- Strategy for the statistical evaluation of a data set of related molecules -- Detailed examples of QSAR calculations on erythromycin esters -- Case studies -- Methods to approach other structure-activity problems.