The atoms that make up ordinary matter fall down, so do antimatter atoms fall up? Do they experience gravity the same way as ordinary atoms, or is there such a thing as antigravity? Recent results, which measured the ratio of antihydrogen's unknown gravitational mass to its known inertial mass, did not settle the matter. Far from it. If an antihydrogen atom falls downward, its gravitational mass is no more than 110 times greater than its inertial mass. If it falls upward, its gravitational mass is at most 65 times greater. What the results do show is that measuring antimatter gravity is possible, using an experimental method that points toward much greater precision in future.

Source: Does antimatter fall up or down? Fi...toms of antimatter interact with gravity