The bioconversion of polyunsaturated fatty acid triacylglycerols to hydroperoxides by the bienzymatic system consisting of lipase (EC 3.1.1.3)/lipoxygenase (EC 1.13.11.12) was investigated in a compartmentalized medium (octane/buffer pH 9, v/v = 1/5). The presence of an organic phase (octane) in the system allowed high solubility of acylglycerols and a well-controlled partition of the components in the medium. Triacylglycerols were solubilized in octane and hydrolyzed by the lipase at the interface with the aqueous phase. Liberated polyunsaturated fatty acids then transferred to the aqueous phase and reacted with lipoxygenase. The products of this second reaction, hydroperoxides, were hydrophilic and therefore remained in the aqueous phase. Behavior of the two successive enzymatic reactions and their dependence on the surrounding media were studied in a multiphasic reactor. Total yield : [hydroperoxide]/[triacylglycerol] was studied as a function of the system conditions and with different enzymes and substrates. High yields were obtained especially when rising trilinolein as substrate in the presence of lipase from Mucor javanicus and the soybean lipoxygenase-1.