In updating of an earlier paper, this review extends comparisons between the reported physicochemical properties (both experimental and theoretical) of the six aromatic thienopyridine systems and their benzopyridine and benzothiophene isosteres. Systems covered are primarily thieno[2,3-b]-, -[3,2-b]-, -[2,3-c]-, and -[3,2-c]pyridines (1-4, respectively), quinoline (Q), isoquinoline (IQ), and benzo[b]thiophene (BT), with very limited attention to the less stable thieno[3,4-b]- and -[3,4-c]pyridines. Dipole moments, ^l3C nmr measurements, mass spectra, molecular complexation, and keto-enol tautomerism are discussed. Reissert, Reissert-Henze, and Hamana reactions which introduce carbon-bonded substituents into the pyridine ring, and addition reactions to the thiophene ring of sulfones are covered. Also electrophilic reactions, nucleophilic displacements, lithiation, and (for thienopyridine 1 only) free radical substitutions are noted. With few exceptions, notably the positions of substitution (α for Q, γ for 1) in the Hamana reaction and the differences in reactivities of the α- and γ-chloro groups toward nucleophilic displacement (γ _≡ α for Q, γ > α for 1 and 2), the generalization that the chemistries of 1-4 are interpretable as amalgamations of those of their isosteric reference compounds (Q or IQ, and BT) is strongly supported. Even in a sample of a fossil fuel, GC-MS analysis implies that one finds structurally closely related condensed thiophene and thienopyridine components. Moreover, various examples of thienopyridine isosteres of biologically active molecules are known or suspected agonists or antagonists.