The products of Fischer-Tropsch synthesis boiling below a separated decant oil fraction are subjected to cooling to a temperature of about 100.degree. F and separation of the cooled product to recover Fischer-Tropsch produced water comprising oxygenates, a normally liquid hydrocarbon phase comprising absorbed oxygenates and a gaseous phase normally comprising a substantial amount of C.sub.5 hydrocarbons in combination with lower boiling materials including unreacted synthesis gas and carbon dioxide. Each of said gaseous phase and said normally liquid hydrocarbon phase are thereafter contacted with a selected crystalline zeolite catalyst particularly selective for the formation of gasoline boiling material of high octane.