Department of Chemistry, University of Delhi, Delhi-110 007 Manuscript received 6 July 1981, revised 11 May 1988, accepted 12 October 1988 The kinetics of the reaction between o-cresol and acetone was studied at 30, 35, 40 and 45±0.05" in 100% benzene. The different hydrochloric acid concentrations used were 0.0176, 0 0314, 0.0512 and 0.0727 M. The reaction was Investigated with and without a promoter thioglycollic acid and taking Into account the functionality (n) of o-cresol. The reaction was found to follow second order rate law and the rate of the reaction was found to Increase with an increase in catalyst concentration. The activation parameters for the overall reactions have been calculated. The reaction was investigated In various solvents like benzene, chlorobenzene and methanol. The overall rate constant was resolved Into step rate constants. The results have been compared with those of o-cresol- formaldehyde reaction