The official International Dairy Federation method tor determination of the peroxide value of anhy drous milk fat was extended to meat, fish and vegetable oils. The ferrous oxidatlon-xylenol orange method for determination of peroxide val ues of liposomes and lipoproteins was modified to make it simpler more rapid. These 2 spectro- photomctric mcthods wcrc used successfully to de- termine the peroxide values of beef, chicken, but products. The results in most cases were consistent vith those obtained by using the AOAC Official Method. The spectro- photometric methods have an assay time of less than 10 min, require s0.3 g fat, and are capable of determining low as 0.1 mequiv/kg of sample.