Abstract: A method of growing crystalline cadmium mercury telluride by a vertical Bridgman process. A problem in growing such crystalline material is to produce significant quantities of material which are both of acceptable crystal quality and are of homogeneous composition. A melt of cadmium mercury telluride is prepared in a sealed ampoule, and the crystalline cadmium mercury telluride is grown from the melt by a vertical Bridgman process at a rate of from 0.1 to 2 mm per hour. During growth the ampoule is subjected to an accelerated crucible rotation programme which comprises the steps of accelerating the rate of rotation of the ampoule about is longitudinal axis and decelerating the rate of rotation of the ampoule.