In this work inorganic membranes used for whey protein fractionation were cleaned with enzymatic detergents. The inorganic membrane Carbosep(R) M1 (Orelis S.A., France), of 150 kg/mol molecular weight cut-off and ZrO2 filtering layer, was used and the commercial detergent P3-Ultrasil(R) 62 (Henkel lberica S.A., Spain) was selected for the cleaning. Hydraulic and chemical methods were considered to characterize the membrane cleanliness. Cleaning efficiency was observed to be a function of the operating conditions: recycling versus non-recycling of permeate, cleaning solution pH. enzymatic agent concentration and cleaning time. The optimum conditions to perform the cleaning were related to the optimum conditions to hydrolyze whey proteins in a batch reactor. Very high cleaning efficiencies (similar to100%) were reached in short operating times (20 min). However, residual matter was detected on the membrane surface after the cleaning. (C) 2004 Elsevier B.V. All rights reserved.