Abstract: A fuel composition for spark-ignition engines consisting essentially of gasoline and a barium compound in an amount of 100 ppm or more in terms of barium metal and relative to the gasoline, said barium compound being selected from the group consisting of a barium sulfonate, a barium naphthenate, a barium alkylsalicylate and a barium .alpha.-alkylalkane monocarboxylate. Spark-ignition engines utilizing this fuel composition operate with improved characteristics relative to adhesion of carbon to the spark plugs. The exhaust from the engine does not degrade the exhaust gas purifying catalyst even when the engine is equipped with an exhaust ignition control device.