Geometries and energies of small proton-bound symmetric dimers and minimum energy pathways for the proton transfer from one subunit to the other were calculated both at the semiempirical MNDO/PM3 and at ab initio HF and post HF levels. Except for systems, in which carbon atoms are involved or oxygen atoms are part of acceptor molecules, PM3 can be used for a good quantitative description of hydrogen bonds near the equilibrium geometry. If the subunits are separated by more than 2.5 , attractive forces will be lost quickly. Proton transfer reactions are modeled in a qualitative acceptable manner. The global barrier of proton transfer rises as well as the calculated association enthalpy of the hydrogen bonded dimer rises. If proton transfer occurs between nitrogen acid/base pairs, PM3 barriers of activation are about 5 - 10 kcal/mol higher than corrected ab initio results. Two dimensional slices through the potential energy hypersurfaces of proton transfer of two systems described in the paper. Energy values are in kcal/mol relative to the grid point with the lowest energy. Points signed with M represent equilibrium structures, those signed with S are saddle points of first order.