Conclusions: On the basis of AOM tests run to date it appears that 2,4,5‐trihydroxyphenones are quite potent antioxidants for many applications. Some of the lower members of the series, such as 2,4,5‐trihydroxybutyrophenone, are outstandingly effective in lard, paraffin wax, mineral oil, and peanut oil. In other media, such as cottonseed oil, corn oil, castor oil, sesame oil, and tallows, they are less effective but still fairly active. In greases, palm oil, and sperm oil, they are only moderately effective. Over‐all the 2,4,5‐trihydroxyphenones compare quite favorably with current commercial products. It would appear that as more testing is done, more applications for these compounds may be found.Subacute toxicity studies made with 2,4,5‐trihydroxyacetophenone and 2,4,5‐trihydroxybutyrophenone indicate that they are of a low order of toxicity. Long‐term feeding tests on rats and dogs are underway with the butyrophenone, and after four months there are no apparent ill effects.