A method is suggested to utilise the ‘Restoring force balance’ criterion of Redington and Aljlbury along with one set of isotopic frequencies for the evaluation of molecular force fields by Parametric Representation method. Fluoroform and formaldehyde molecules are taken as illustrations. In order to check the validity of the method other molecular constants such Coriolis coupling constants, mean amplitudes of vibration and rotational distortion constants are calculated and compared with those of earlier workers.