A detailed study of the thermal non-catalytic hydrolysis of sunflower oil with subcritical water is illustrated. A number of experimental runs were conducted in a tubular reactor over a range of temperatures (270-350 degrees C) and reaction times (up to 30 min) at 20 MPa. The influence of temperature on the kinetic parameters was determined by applying the Arrhenius equation to the optimum evaluated rate constants. The energy of activation was found to be highest in the first hydrolysis reaction (triglyceride). The yield of fatty acid was found to increase dramatically with a rise in temperature, which then acts as an acid catalyst into the hydrolysis reactions. A kinetic model is proposed for the thermal hydrolysis of sunflower oil, which elucidates the reaction mechanism at different reaction temperatures and reaction times. The proposed kinetic model fits well with the experimental results with a maximum variance of <5.4%. Crown Copyright (C) 2008 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved.