Two different expressions for the solvent reorganization energy for the heterogeneous electron-transfer reactions at an ITIES have hitherto been derived by Kharkats (Sov. Electrochem., 12 (1976) 1257) and by Marcus (J. Phys. Chem., 94 (1990) 1050). To settle the controversy, a detailed calculation of this energy is presented. The result obtained corroborates that published by Marcus. A generalization for different geometries is also included.