The hydrolysis process of the cisplatin analog cis-dichloro(ethylenediamine)platinum(II) (cis-DEP) was theoretically investigated at the Hartree-Fock, density functional theory and the second order Moller-Plesset perturbation theory levels of calculation. The stationary points on the gas phase potential energy surface for the first and second hydrolysis steps were fully optimized and characterized. For the first aquation process the gas phase results are in satisfactory agreement with the experimental data. However in order to reproduce the observed rate constant for the second hydrolysis step it is essential to include the solvent effect. The structures and energetic properties are similar to the values found for the parent compound cisplatin, showing that the cis-DEP analog should be considered as a potential drug concerning its hydrolysis process. (C) 2003 American Institute of Physics.