In the frame of a research project aimed at obtaining high-resistivity CdTe crystals, the authors report on the preparation of (nominally) undoped semi-insulating (SI) CdTe crystals. The method is based on the use of polycrystalline CdTe charges synthesized from 7N pure Cd and Te elements, in such a way as to ensure an atomic stoichiometric ratio (Cd/Te) equal to 1 within the weighing error. The charges are further stoichiometrically adjusted by subliming off residual excess components through effusion in semi-open ampoules vented to vacuum. By making use of these charges, undoped SI CdTe ingots, made up of large single-crystal grains, have been grown from both vapour, by closed-ampoule physical vapour transport and melt, by liquid encapsulation Bridgman technique, The yields in SI material turned out to be 100% for vapour-grown samples and about 50% for melt-grown ones. Preliminary results of this research work are presented here and briefly discussed. (C) 2002 Elsevier Science B.V. All rights reserved.