An ellipsoidal cavity model has been used to study the energy changes in occupied molecular orbitals induced by solute- solvent electrostatic interactions. Some benzene derivatives have been selected as solutes. Calculations have been carried out at the CNDO and ab in itio STO-4G levels. Important variations in the molecular orbital sequence, involving a change in the HOMO nature, have been observed. A perturbation analysis is employed to understand the orbital evolution from gas phase to solution.