Synthesis gas is converted to diesel fuel and a high octane gasoline in two stages. In the first stage the synthesis gas is converted to straight chain paraffins mainly boiling in the diesel fuel boiling range utilizing a catalyst consisting essentially of cobalt, preferably promoted with a Group IIIB or IVB metal oxide, on a support of gamma-alumina, eta-alumina or mixtures thereof. A straight chain paraffin portion of the effluent in the C.sub.5 -C.sub.9 range is converted in a second stage to a highly aromatic and branched chain paraffinic gasoline using a platinum group metal catalyst.