Application of a colorimetric method for determination of lipid peroxides in foods was investigated. We identified the optimal amount of potassium iodide used in the method. It was confirmed that by adopting this optimal amount the method could be satisfactorily applied to triacylglycerols and free fatty acids. Furthermore, in order to extend the scope of its application to phospholipids, we made several additional modifications including replacement of the solvent and established an improved technique applicable to phospholipids having a peroxide value of 40 or more.