The structure of mechanically alloyed (MA)Ti-Si powders has been investigated by means of X-ray diffraction radial distribution functions analysis and computer-generated quasi-crystalline models. It was established that the investigated samples with compositions Ti33Si67 and Ti42Si58 consist of an amorphous matrix, with chemical short-range order (SRO) similar to that of the TiSi phase, in which crystallites of the Ti5Si3 and Ti5Si4 phases are embedded. For the composition Ti44Si56, the SRO resembles the structural arrangement in the Ti5Si3 phase. An attempt has been made to explain these results using the formation enthalpies of the amorphous and the crystalline phases formed in earlier stages of MA. The Ti5Si4 and Ti5Si3 phases have a much lower formation enthalpy than the other Ti-Si phases. That is why the amount of mechanical energy imparted during MA is not sufficient completely to drive the amorphization in these two phases.