A multiple-cylinder spark-ignition internal combustion engine for an automotive vehicle, in which the ratio of the inactive compounds in the mixture gases produced in each combustion chamber to the fuel component in the combustible mixture inducted into the chamber is maintained within a predetermined range and the spark plug for each engine cylinder is arranged so that the flame travel from the spark plug is reduced to a minimum for promoting the combustion reaction to proceed in the least possible time. Improvements are further made in respect of the exhaust gas recirculation rate, the location and measurements of the spark plug, the configurations and measurements of the engine cylinder and the arrangement of the intake and exhaust ports so as to reduce the concentrations of toxic compounds in the exhaust gases without impairing the performance efficiency of the engine.