Light microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis combined with macro and microhardness measurements were performed to characterize a hard layer (alpha-case) forming on the surface of Ti-6Al-4V surgical implants castings. The thickness of alpha-case was found to be approximately 200 mu m, while its hardness was two times higher than the hardness in the core of castings. No presence of the beta phase was detected in the alpha-case.