A novel, enzymatic, porous silicon (PS) based potentiometric method for estimating triglycerides is reported. Lipase, an enzyme, which hydrolyses triglycerides was immobilised on PS which was prepared from p-type (100) crystalline silicon and was thermally oxidized. On hydrolysis the triglycerides result in the formation of fatty acids which causes a change in the pH of the solution. Enzyme solution-oxidized PS-crystalline silicon structure was used to detect changes in pH during the hydrolysis of tributyrin as a shift in the capacitance-voltage (C-V) characteristics. Optimisation of the conditions for the enzymatic reaction and calibration of the sensor are included. (C) 2002 Elsevier Science B.V. All rights reserved.