This is a process for the production of synthesis gas substantially free from entrained particulate carbon. The product gas is preferably produced substantially free from volatile hydrocarbon contaminants. A feedstock comprising fresh liquid hydrocarbon oil is introduced into a distillation zone and separated into a light liquid hydrocarbon fraction and a heavy liquid hydrocarbon fraction. The light hydrocarbon fraction in admixture with a preheated slurry produced subsequently in a gas scrubbing zone and comprising particulate carbon and said heavy liquid hydrocarbon fraction are introduced into the reaction zone of a free flow noncatalytic synthesis gas generator and reacted by partial oxidation with oxygen and steam at an autogenous temperature in the range of 1,500*-3,000* F. to produce synthesis gas comprising hydrogen, carbon monoxide, and appreciable amounts of entrained particulate carbon. The effluent gas from the reaction zone is cooled by indirect heat exchange and is then scrubbed free of said entrained particulate carbon in a gas scrubbing zone with said heavy liquid hydrocarbon fraction and carbon slurries thereof. The scrubbing zone is preferably maintained at a temperature and pressure so that undue stripping of volatile fractions from the scrubbing fluid is prevented. When desired, water and any vaporized hydrocarbon in the overhead from the scrubber may be condensed out and separated from the product gas stream.