In a recent paper' in this Journal, "High-pressure Liquid Chromatographic Assay of Benzoyl Peroxide in Dermatological Gels and Lotions," the authors questioned the validity of a TLC system described by our laboratories in a paper2 entitled "The Stability of a Benzoyl Peroxide Acne Cream Product." The reliance on removing and measuring spectrophotometrically an extract from the solvent front of a chromatogram was recognized, and a subsequent paper3, "An Improved TLC Procedure for the Quantitative Determination of Benzoyl Peroxide in Acne Creams," was published. This procedure utilized acetonitrile-water (1:l) in a reversed-phase system on an acetylated support, and complete resolution was achieved with benzoyl peroxide (Rf 0.42), benzoic acid (Rf 0.9-LO), and other isolable impurities. Excellent assay agreement was obtained between this method and an iodometric titration procedure in deliberately degraded cream formulations. The fact that the iodometric titration procedure was proven to be stability indicating suggests its use as an assay method in terms of economics and simplicity over chromatographic methods.