By means of the horizontal modified Bridgman technique, CdTe and CdZnTe crystals have been grown. The conditions of synthesis have been described and a modified gradient freeze technique has been experimented and proposed. By modifying the transverse gradient, nature of the boat, gas overpressure and temperature cycles, different growths have been compared. A computerized power recording was found to be extremely sensitive in spotting any thermal accidents. With an optimization of these different factors, we have obtained large single crystals: they gave (111) substrates up to 28 cm2. A new and fast optical technique with a He-Ne laser has been used for studying all orientation parameters. The substrates have been characterized by double X-ray diffraction, photoluminescence and electrical measurements. © 1989.