Abstract: A fuel vaporizer for an internal combustion engine comprises an air/fuel heating and mixing chamber which vaporizes liquid hydrocarbon fuel to a heated, dry vaporous state and mixes it with heated air for introduction of the mixture into a primary or main air stream for supply to the cylinders of the engine. A first form of the vaporizer uses exhaust gas from the engine to heat the fuel and air, and a second form of the invention uses electrical resistance elements to heat the fuel and air. Both forms of the invention include supplemental vaporized fuel supply devices operable during acceleration and starting.