A set of 25 4'-, eight 2',4'-, and five 2',4',6'-substituted 4-aminodiphenyl sulfones were tested for their inhibitory activity on dihydropteroate synthase of Escherichia coli. Linear regression analysis shows that enzymic inhibition indices correlate well with both quantum chemical and spectroscopic descriptors of the electronic structure of the common moiety 4-NH2-C6H4-SO2 of the sulfones (the above descriptors being expressed in relation to the electronic structure of the enzyme substrate, p-aminobenzoate). Therefore, the biological activity of the sulfones can be related to the electronic structural resemblance between these inhibitors and the substrate of the target enzyme. Since a similar result was previously obtained for a wide series of sulfanilamides in their different (amidic, imidic, and anionic) forms, it appears possible to consider the antibacterial sulfones and sulfanilamides as a congeneric chemical series. On the basis of the present results, the classical theory of antimetabolites would appear to take on a quantitative and sound rationale.