Linalyl acetate and undecylenic acid were studied to determine their abilities to reduce oxidative changes in soybean oil held at frying temperature. All compounds to be tested were added to soybean oil and heated to 180 "C for 56-70 h. Fatty acid changes and conjugated diene formation were monitored. Acetylation of linalool to linalyl acetate (LA) caused the formation of many byproducts, which were separated by thin-layer chromatography into three bands. The materials isolated from the bands were tested and found to be equally effective antioxidants. Purchased LA had an antioxidant effect similar to that of the bands. The LA materials from the bands were further purified and identified by GC-MS. All the effective compounds were similar in structure to LA. Undecylenic acid provided some protective effect but less than that of LA, which had less antioxidant effect than i17-avenasterol and poly- (dimethylsiloxane).