A simplified valence force field has been developed for some molecules containing the CC group by using the overlay technique. In constructing the force field special attention was paid to the transferability of the force constants since they are intended to be used in large molecules. The force field contains 57 parameters out of which 22 are transferred from other overlay force fields and 35 are optimized using 200 experimental frequencies. The root-mean-square frequency error is 10.5 cm −1 which includes the CH strecthing vibrations.