Abstract: An equation of quantitative structure-activity relationship for the central nervous system depressant, 2-Imidazolidinone derivatives, has been established by the method of molecular connectivity. It is compared with Eric's equation for the same series of compounds set up by the Hansch method and it has been found that our equation has a more significant correlation than the latter. Besides, the effect of quantitative structure factors on the magnitude of drug activity is also discussed.