The transfer of a proton between two potential wells, as in a hydrogen bond, has been extensively studied. However, transfer under the influence of an electric field has been studied to only a Very limited extent. We have used the system methylamine-proton-methylamine to help understand this type of transfer. It is a fairly realistic model of systems that are of importance (e.g., amino acids) and is small enough to calculate. The potential energy surface for the system has been determined by ab initio calculation, using Gaussian 94, and the wave function of the proton then found using the three-dimensional Fourier grid Hamiltonian method. The proton is transferred, with the aid of an external electric field, from a potential well approximately 1 Angstrom from one methylamine nitrogen to a well neighboring the other when the two nitrogens are constrained to remain either 3.2 Angstrom or 3.6 Angstrom apart. When the methylamines are allowed to optimize without constraint, they form a potential surface for the proton such that the proton is shared between the two molecules. Under conditions in which the methylamines are constrained to be further apart than optimal, two separate potential wells are formed which localize the proton in one or the other. The levels can be matched or mismatched by application of an external electric field. The proton will pick the lower energy well; as the field causes the energy in the upper well to drop below what had been the lower level previously, the proton shifts. We have found that a field shift of less than 10(5) V m(-1) causes a shift of the wave function peak from 15:1 in one direction to a correspondingly complete shift in the other direction, with the 3.6 Angstrom separation; the field change needed is also small, but a bit less so, at 3.2 Angstrom. The switching field is superimposed on a considerably larger field due to the asymmetry in the wells. We do not calculate the transfer rate; the calculation should apply as long as the rate of field change is slower than the transfer rate.