The kinetics of acetophenone-phenylhydrazine reaction has been studied spectrophotometrically in different solvents and solvent compositions. The effect of various substituents on acetophenone and the effect of changing dielectric constant on the rate of the reaction have been studied by employing different dipolar and aprotic solvents. The rate data were fitted into the extended linear free energy relationship (LIFER) equation and the inductive-resonance substituent constants have been evaluated. It was inferred that higher the polarity of the medium in each of the solvents employed, the magnitudes Of substituent constants increased and saved the resonance contribution of substituted acetophenones.