Titanium silicide has been formed by ion implantation of titanium into high purity silicon (111) and thermally annealed in ambient Ar. Cross-sectional transmission electron microscopy (XTEM) shows that the silicon annealed at 1000 degrees C consists of three parts : an intermittent C54-TiSi2 layer, a region of buried C49-TiSi2 precipitates and a residual radiation- damaged zone. For the sample annealed at 700 degrees C there is a continuous C54-TiSi2 layer and a zone of buried crystals below the silicide layer. After thermal annealing at 800 degrees C for 30 min, only a continuous C54-TiSi2 layer is present in the silicon substrate surface and its orientation relationships are determined as [121]C54-TiSi2 parallel to[110]Si and (111)C54-TiSi2 parallel to(111)Si. High resolution electron microscopy (HREM) reveals that there is a transition layer which may relax the strain caused by the lattice misfit between the C54-TiSi2 film and the silicon substrate.