Three-phase hydrogenation of mixtures of styrene and 1-octene in toluene was carried out in a monolithic reader. A cordierite monolith with an alumina washcoat, impregnated with Pd, was used as catalyst Operating conditions wee in the range of 43-80 degrees C and 0.5-1.5 MPa. The linear velocities and the liquid-gas ratio were varied in the range of 0.05-0.45 mis and 1:1-6:1 m(3)/m(3), respectively. Styrene was preferably hydrogenated to ethylbenzene, while 1 major part of the initial quantity of 1-octene was isomerized to internal olefins. Formation of alkylcyclohexanes was negligible under all process conditions used The observed hydrogenation rates for styrene were high compared to values listed in literature. Results indicated that external mass transfer was the rate limiting step. Furthermore, incomplete or non-uniform wetting may have been limiting conversion, especially at low liquid loadings. The experiments prove that the monolithic reactor is an attractive alternative for conventional three-phase readers.