The objective of this study is to investigate the boriding behaviour of titanium implant materials on the basis of their crystalline structure and chemical composition. alpha-type Cp-Ti, alpha + beta type Ti-6Al-4V and beta-type Ti-45Nb alloys have been borided by the powder-pack boriding technique at temperatures between 850 and 1200 degrees C. The X-ray diffraction, GDOES and SEM analysis demonstrated that boride layers on Cp-Ti and Ti-6Al-4V alloy mainly composed of TiB2 and TiB phases, whereas Ti-45Nb alloy consists of the mixture of TiB2.NbB2 and TiB phases. Boride layers on Ti-45Nb alloy grew uniformly and the highest boride layer thickness of 72.1 mu m was obtained on this alloy among the others. Activation energies of boron in monolithic layer of Cp-Ti and Ti-6Al-4V alloy were determined to be 214.5 and 231.8 kJ/mol, respectively. Activation energies in monolithic and total boride layers on Ti-45Nb were determined to be 228.5 and 145.8 kJ/mol, respectively.