A catalyst system for the conversion of synthesis gas in a single stage to liquid hydrocarbons comprises(a) a copper-containing alcohol synthesis catalyst,(b) an iron-containing modifier for the alcohol synthesis catalyst to promote the formation of hydrocarbons, and(c) a metallosilicate wax cracking catalyst.The alcohol synthesis catalyst (a) can contain thorium, zinc, uranium or zirconium in addition to the copper.The iron-containing modifier (b) can contain an iron-containing zeolite such as ferrierite or an inorganic support containing ferrous or ferric ions. The metallosilicate can be a zeolite or gallosilicate. The zeolite can have a pore diameter of at least 5 Angstroms and can have the faujasite structure. A Group VIIIA metal e.g., Pd may be incorporated on the zeolite to suppress coke formation.A hydrocarbon product from the conversion can be obtained containing at least 70 percent by weight of hydrocarbons in the range C.sub.3 to a boiling point of 340.degree. C., and less than 10 percent by weight of methane.