6-O-Monolinoleoyl trehalose synthesized by the immobilized-lipase-catalyzed condensation of linoleic acid and trehalose was dissolved in water at various concentrations, and its oxidation processes were then measured at 35 degrees C based on both the decrease in the linoleoyl residue and oxygen consumption. The stoichiometric coefficient of oxygen to the linoleoyl residue was in unity except during the late stage of the oxidation. The oxidation process could be expressed by the rate equation of the autocatalytic type. The rate constant was higher for the higher substrate concentration, but it was not in proportion to the concentration at substrate concentrations higher than its critical micelle concentration. These results suggested that the migration of oxygen into the hydrophobic core of the linoleoyl residues through the hydrophilic trehalose layer of the linoleoyl trehalose micelles affected the overall oxidation rate of the linoleoyl residue.