A study of a diffusion couple of pure iron and titanium has been carried out at 850°C for 4H. XRD analysis on the surface of samples reveals the presence of both phases Fe2Ti and FeTi. A β titanium layer was also identified by XRD. A shift between theoretical and measured diffraction peaks was noticed. This peak shift is due to the high concentration of iron (17 % at.) in the β titanium. The High resolution SEM micrographs show the β layer in the titanium sample. This layer is homogeneous for Fe concentrations between 8 % and 17 % at. Then this layer transforms partially in α + β for Fe concentrations between 5 and 8 % at., with a Widmanstätten structure . The β titanium layer growth fits well with models described in the literature . The High resolution SEM micrographs shows also in the Fe sample a solid solution of Fe(Ti), Fe2Ti precipitates and small pores that could be Kirkendall voids.