A kinetic study of the reaction of phenol with formaldehyde has been carried out at temperatures of 65° ± 0.05°C, 70° ± 0.05°C, 75° ± 0.05°C, and 80° ± 0.05°C using hydrochloric acid as catalyst. The pH maintained was 1.14, 1.32, 2.20, and 3.00. The reaction follows a second-order rate law. The rate is found to increase with decrease in pH. The overall rate constants are resolved into step rate constants. The values of the Arrhenius parameters and the entropy of activation for the overall reaction as well as for the step reactions have been calculated. A mechanism conforming to the energies and entropies of activation of the reaction has also been suggested.