Department of Chemistry, A. N. College, Patna-800 013, India E-mail: biharisingh@rediffmail.com Manuscript received 13 October 2000, revised 3 August 2001, accepted 20 August 2001 Kinetic study of the hydroxide anion catalyzed hydrolysis of ethyl caprylate has been done in water-DMSO binary system at various composition (10-60%, v/v) of DMSO and at 20-35°. Specific rate constant values increase with increasing proportion of DMSO at all temperatures. Increase in specific rate constant value with decreasing dielectric constant of the medium supports Parker's view. A reasonable interpretation of variations in specific rate constants and thermodynamic parameters have been put forward on the basis of solute-solvent interaction, solvation of the transition state and bulk dielectric constant of the medium.