Some experimental characteristics of selected simple inorganic outer-sphere electrode reactions which deviate from the expectations of conventional electron-transfer models are discussed so as to identify some extant issues deserving further theoretical and/or experimental examination. Attention is focused on the one-electron reduction of Co(III) ammine complexes in view of their chemical irreversibility, enabling very wide ranges of rate-potential behavior to be evaluated straightforwardly in different reaction environments. Kinetic behavior in homogeneous-phase and interfacial systems is intercompared directly by converting the former to 'equivalent-electrochemical' rate units. Unexpectedly large (up to ca. 10 6 -fold) variations in the work-corrected rate constants for ostensibly outer-sphere Co(III) ammine reductions are observed at a fixed driving force as the reducing environment is altered. The lowest reactivities, observed with inorganic reductants and CO-coated Pt(111), probably reflect in part non-adiabatic pathways. The marked-by (10 3 to 10 4 -fold) faster rates observed on Au(111) (and other Au and Pt electrodes) relative to mercury aqueous interfaces, however, reflect chiefly lower solvation Gibbs energy barriers at the former interface. These differences apparently reflect variations in the reaction site, as deduced partly by examining unimolecular outer-sphere rates and transfer coefficients. The latter measurements also indicate the presence of asymmetric barriers, associated with electron transfer-induced changes in inner-shell force constants. The interpretation of unexpectedly large D/H isotope effects in terms of solvent reorganization is also discussed in relation to recent molecular-dynamics predictions.