In the diamond growth by temperature gradient method under high pressure and high temperature, the growth of a high-quality diamond crystal without metal inclusions has been investigated. Large high-quality type IIa diamond crystals without impurities of 7-8 ct (about 10 nun across) can be grown at a high growth rate of 6-7 mg/h by prolonged maintenance of a high-precision temperature control with an adequate selection of solvent metal and additives. Type Ib diamond crystals containing nitrogen impurities can be grown at higher growth rates up to 15 mg/h by using large seed crystals and adjusting the morphology with temperature control. This large seed method is not applicable for growing a type Ha diamond crystal because it is hard to control the crystal morphology of it. (C) 2002 Elsevier Science B.V. All rights reserved.