A method was developed to prepare a crystalline structure of beta-TiCl3 (brown) using an electron-donor compound as an internal Lewis base, namely, diisoamyl ether (DIAE). beta-TiCl3 combined with triethylaluminium (TEA) resulted in highly active and stereospecific catalyst systems close to those based on violet TiCl3 (alpha-, gamma- or delta-TiCl3) for propylene polymerization. Thr influence of solvent and amount of Lewis base employed in the catalyst synthesis on the catalyst properties and structure was investigated. The catalyst structure was examined by X-ray diffraction.