To provide a motorcycle exhaust system, which is less susceptible to the elevated temperature of the exhaust gases and vibrations induced by the motorcycle combustion engine (E) and in which the sectional area of the exhaust passage can be properly adjusted independence on the operating condition of the motorcycle combustion engine (E), the motorcycle exhaust system includes a motorcycle combustion engine (E) mounted at a location generally intermediate between front and rear wheels (3 and 9), an exhaust passage fluidly connected at one end with an exhaust port of the motorcycle combustion engine (E), a silencer (17) fluidly connected with the opposite end of the exhaust passage and supported by the motorcycle frame structure (FR) at a location generally above the rear wheel (9); and an exhaust control valve (24) disposed in an inlet of the silencer (17) for variably adjusting the sectional area of the exhaust passage.