Lipoxygenase (LOX) is an enzyme that regioselectively introduces the hydroperoxide functionality into polyunsaturated fatty acids, such as linoleic acid (LA). Hydroperoxide derivatives of polyunsaturated fatty acids are of interest because they can serve as important intermediates in the synthesis of chemical and pharmaceutical compounds. In this study, LOX was immobilized in dispersed phyllosilicate layers that were cross-linked with silicate polymers formed by the hydrolysis of tetramethyl orthosilicates. The effects of substrate concentration, reaction temperature and solvent participation were studied on the oxidation of LA by LOX. The temperature optimum for the oxidation of LA by immobilized LOX was 25 degrees C and values of Km and Vmax for this reaction were 1.7 mM and 0.023 micromol/min respectively. Enzymic activity was stimulated by the addition of 10% (v/v) iso-octane to the reaction mixture. The immobilized LOX preparation showed a degree of substrate preference that demonstrated that 1,3-dilinolein was a better substrate than LA in the oxidation reaction, followed in order by 1-monolinolein, methyl oleate and trilinolein. In general, LOX immobilized in cross-linked phyllosilicates retained the physical and chemical characteristics of free LOX.