An exhaust system for internal combustion engines includes at least two exhaust passages, each passage communicated with at least one branch exhaust passage of an exhaust manifold communicating exhaust ports of a multiple-cylinder engine, and a confluent exhaust passage disposed downstream of said at least two exhaust passages, said confluent exhaust passage including a confluent point for converging downstream ends of said at least two exhaust passages. The exhaust system also includes a communication passage substantially parallel with the at least two exhaust passages and a valve disposed in the communication passage, for allowing a portion of exhaust gas flow to bypass said confluent point only when the engine is within a predetermined high engine revolution range.