A theory of in situ tunneling microscopy of redox molecules in the case of the fully adiabatic electron transitions is suggested within the spin-less model. The theory is based on the thermal averaging of the tunneling current over the adiabatic Gibbs energy surface (AGES) and permits to describe crossovers from the thermally activated regime to the adsorption regime and from the small bias voltage limit to the large bias voltage one. It also permits the calculations of the tunneling current in the electronically and spatially non-symmetric cases. A number of relationships for AGES and the total tunneling current as a functions of the overvoltage and the bias voltage are established. The concept of the effective overvoltage, which generalizes the concept of the ordinary overvoltage to the case when the stationary current flows in the in situ STM system, is introduced. The kinetic regime diagrams, which describe the different types of the electron transfer processes, are constructed within the space of the parameters of the system for the case of in situ STM of redox molecules. The results of calculations of the tunneling current as a function of the parameters of the system are presented, discussed and compared with those in literature. (c) 2006 Elsevier B.V. All rights reserved.