In a process of producing a synthesis gas which has a low inert gas content and is intended for the synthesis of alcohols, particularly of methanol, and of hydrocarbons, and which is produced from coal or heavy hydrocarbons, by a gasification under pressure with oxygen and steam, whereafter the raw gas is cooled, the impurities are removed by a scrubbing with methanol, and the methanol is removed by means of molecular sieves from the cold pure gas. The pure gas is then cooled further and partly liquefied, the remaining gas is further cooled by a pressure relief and methane is distilled from the liquid part with simultaneous recovery of the synthesis gas, which consists of hydrogen and carbon monoxide and has a low methane content. All or part of the methane is compressed and is subsequently reacted with steam and oxygen to produce carbon monoxide and hydrogen. The produced gas is admixed to the synthesis gas or to the partly purified raw gas.