The compound, 3-methylnonane-2,4-dione (MND), has an intense odor when evaluated at the outlet of a gas chromatograph. Sensory evaluation of MND in a mineral oil/water emulsion system showed that its flavor intensity increased almost imperceptibly with increased concentration (from 0.09 to 2.56 ppm), and just above threshold. Also, the concentrations of MND in soybean oils at various peroxide values were between 0 to 0.804 ppb, which were far less than concentrations tested in a mineral oil/water emulsion during sensory evaluation. These results do not support the theory that MND contributes strongly to the reversion flavor of soybean oil. On the other hand, freshly deodorized soybean oil has a characteristic nutty flavor. The possible volatile flavor compounds existing in fresh soybean oil were investigated, but none of these compounds was present in enough quantity or had a flavor impact that would account for the fresh flavor of deodorized soybean oil. Small particles could be generated in the human mouth that might provide a mechanism to bring oil with nonvolatile flavor components into contact with the olfactory organ. Attempts to separate possible nonvolatile flavors in deodorized oil from triacylglycerides by chromatography on alumina or reaction with 2,4-dinitrophenylhydrazine were unsuccessful. Possibly the nutty flavor of freshly deodorized soybean oil is caused by the glycerol esters themselves.