Drug activity is dependant on both the fine and gross structure of the molecule. In this study, the properties of the molecule that are dependant on its fine structure, such as dipole moment, ionization potential, and energies of the HOMO and LUMO were calculated for the optimized geometry of some drugs using Ab initio method and the GAMESS program. This systematic analysis demonstrated that, for the nonprotonated forms, the structural parameters IP and DE are the best correlators with log A and the correlation with D is nonsignificant. Mathematical relations between the activity and the structural parameters were derived for the studied drugs. The gross properties of the molecule, such as size, geometry, and lipophilicity were noted as important factors in determining the drug activity. References and tables