Electron transfer reaction rate constants at semiconductor/liquid interfaces are calculated using the Fermi Golden Rule and a tight-binding model for the semiconductors. The slab method and a z-transform method are employed in obtaining the electronic structures of semiconductors with surfaces and are compared. The maximum electron transfer rate constants at Si/viologen(2+/+) and InP/Me(2)Fc(+/0) interfaces are computed using the tight-binding type calculations for the solid and the extended-Huckel for the coupling to the redox agent at the interface. These results for the bulk states are compared with the experimentally measured values of Lewis and co-workers, and are in reasonable agreement, without adjusting parameters. In the case of InP/liquid interface, the unusual current vs applied potential behavior is additionally interpreted, in part, by the presence of surface states. (C) 2000 American Institute of Physics. [S0021-9606(00)70507-1].