The radar systems Cu(NH,) 2 +"+, Fe(CN)6"4 " and Fe 3+t2+ and oxygen reduction have been studied on MoS, surfaces normal to the C-axis and parallel to the C-axis, using rotating disc electrodes under potentiostatic conditions . Current-voltage curves were obtained and apparent exchange current densities (ia ) and rate constants (k,r) have been evaluated. The 1 e and k,, values are one order ofmagnitude larger for the I-C surfaces than for the 1-C surfaces of MoS 3 . Both forward and reverse reactions occurred readily in the case of Cu(NH,),+"+ whereas the reverse reaction was partly or totally blocked in the case of Fe(CN)6t`-and Fes + t2+ , respectively. The results indicate that surface states and crystal imperfections play a very important role for all these redox reactions . These surface states seem to be connected with Moatoms at edges and steps on the surface where they are directly exposed to the electrolyte . The differences in the electron transfer rate between the two surfaces is attributed to the greater overlapping of the electron orbitals of the conduction band at the 11 -C surface of MoS, with the electron orbitals of the redox systems, than of those at the 1-C surface.