The technique of ripple injection has been proposed for refueling in tokamak reactors. The usefulness of ripple-assisted fueling has been investigated by using an orbit-following Monte Carlo code. The penetration depth strongly depends on the beam energy. The ripple-enhanced outward flow of ripple-detrapped fast ions is not a serious problem. If Eb/Te0 ≤ 4 is chosen, the fuel efficiency becomes >80%. There is an optimum toroidal angle of the injection beamline to enhance the penetration depth of fast ions, and the range of angles that are effective for fueling is rather wide. The loss of alpha particles incident to the fueling has also been investigated by using the same code. By regulating the shape of the ripple-well region, the total alpha-particle loss can be reduced to <5%. Ripple-assisted fueling in the International Thermonuclear Experimental Reactor (ITER) has also been investigated. Because of the small aspect ratio, the field ripple is strongly decayed in the plasma. Consequently, central fueling presents some difficulties in ITER. However, fueling near one-half of the plasma minor radius is possible with an ∼6% alpha-particle power loss.