Recent results about Fischer-Tropsch (FT)-synthesis, obtained with newly available research tools, allow for an advanced understanding of the unique regime of Fischer-Tropsch catalysis, where CO and hydrogen enter and a hydrocarbon liquid mixture exits the reactor. Obviously, a multistep conversion is taking place on the catalyst surface. Rules, which govern the regime, become visible and among these spatial constraints and frustrated reactions-indicating specific reaction barriers-apparently dominate the system. Of course, an appropriate theory would require knowledge about both the active sites and the reaction intermediates Substantial evidence about both these aspects is becoming available. (C) 2003 Published by Elsevier Science B.V.