The lattice disorder produced by 42-keV and 75-keV Hg ions implanted in Silicon at room temperature and the lattice location of the Hg atoms were studied by means of the channeling technique with a 2.0 MeV4He+beam. The damage produced was found to increase linearly with ion dose until a saturation value, connected to the ion range, is reached. The number of Si atoms displaced for Hg ion implanted was evaluated and compared with the theoretical expectation. The substitutional Hg fraction is connected to the disorder produced: the replacement mechanism is discussed.