The effect of radial acceleration in a rotating vessel on flame propagation has been investigated experimentally. Methane-air mixture compositions between the lean flammability limit and stoichiometric were studied. The behavior of flame propagation and the extinction mechanism were examined in detail. The flame propagating in a rotating vessel is axisymmetric. Initially it propagates a;dally from the ignition point at one end of the cylindrical vessel to the opposite end. After touching the side wall of the cylindrical vessel the flame starts to propagate radially and is locally quenched at the contact surface with the walls. The axial propagation velocity of the flame under all conditions increases with the rotation rate. When local quenching occurs, the radial flame propagation velocity decreases and the extinction rate increases with increasing rotation rate. The extinction mechanism is a multistep process. The most probable stages in that mechanism are as follows. First, heat loss causes the cylindrical flame to extinguish locally near the walls. Once this happens, the combustion gases, which are in contact with the walls, are cooled and displaced radially under the action of centrifugal forces. They flow towards the region of the fresh mixture, which remains in contact with the previously extinguished flame. Differential buoyancy forces the cool gases to move ahead of the flame, which is then extinguished because it is now propagating into a partially diluted nonflammable mixture. The extinction wave propagates along the cylindrical surface of the flame to complete extinction.