Reactor designs for Fischer-Tropsch synthesis (FTS) are illustrative for the struggle to combine the process needs concerning selectivity, heat removal, pressure drop and catalyst attrition and separation. A novel reactor type, the Monolithic Loop Reactor, may constitute a way out of these problems. Experimental data about activity and selectivity of monolithic catalysts are presented. The results show, besides competitive activity and chain growth probability, high olefin to paraffin ratios. (C) 2003 Elsevier Science B.V. All rights reserved.