Abstract: A system for reducing discharge of fuel vapor from a fuel tank of an internal combustion engine to the atmosphere. The system has only one canister which is connected at one side to a top portion of the tank and to the neck of the refueling opening portion of the tank by separate channels, and which is connected at its other side to a suction system of the engine by a purge channel. The system also has three-way electromagnetic valves which are respectively disposed in the channel connected to the neck of the refueling opening portion and in the purge channel, thereby controlling the flows of fuel vapor and purging air.