An interlaboratory study was carried out to determine the feasibility and reliability of a method using the hamster cheek pouch as a model for assessing the potential irritative properties of substances intended to be applied to the lips or other mucous membranes. The test substances were applied once daily to both pouches for 14 consecutive days. Local and general tolerances were appraised throughout the study. At the end of the study, histologic examination of the pouches and the main organs was performed. Results of the feasibility study, conducted on various types of commercial products, indicated that this model is suitable for preparations of various consistence and composition. Results of the reliability study, carried out on gel-type preparations containing various concentrations of a known irritant, sodium lauryl sulfate, indicated that the method elicits a dose-dependent reaction for this compound. This hamster cheek pouch method was reproducible for the various parameters under consideration: local tolerance, general tolerance, histologic examination. For all products, results were in good agreement among the various laboratories participating in the study. The French regulatory authorities of the Fraud Repression Department have accepted it as an official method for the evaluation of the potential irritative properties of cosmetics and hygiene products intended to be applied to the lips or other mucous membranes.