The influence of radiative heat transfer on the temperature fields in the crystal and the shape of the melt/liquid interface in Czoehralski sillenite BGO growth is considered. It is shown that specular reflection at the shoulder side surface results in a large convexity of the interface and the appearance of a thin cool region near the crystal axis. The latter phenomenon is explained by poor conductivity and rather appreciable absorption coefficient of sillenite crystals and may be responsible for the formation of a dark core in the crystal center. (C) 2004 Elsevier B.V. All rights reserved.