Based on results of MP2/6-31G* ab initio calculations an MM2 molecular mechanical parameter set has been developed for molecules containing N(sp3)-O(sp3) single bonds, existing parameters concerning the other bonds being retained. The new parameter set was tested for small organic compounds. A simple, generally applicable multilinear regression algorithm has been used and a program written to complement an existing force field (e.g. MM2) with such parameters extracted from quantum chemical computations.