Abstract: In a dil.H3PO4 solution,potassium iodide was oxidized by benzoyl peroxide to give iodine quantitatively.A blue colored complex was formed by the reaction of the liberated iodine with starch,and its absorption measured at 585 nm,the absorption maximum of the blue colored complex.Linear relationship was kept within 0.016 g·L-1 of benzoyl peroxide.As an indirect photometric method for the determination of microamounts of benzoyl peroxide,it was applied to the analysis of wheat flour samples,and values of recovery over 93.3% were obtained.