Bismuth germanium silicon oxide (BGSO) mixed crystals have been successfully grown from solid solutions of bismuth germanium oxide (BGO)-bismuth silicon oxide (BSO) melt by the Czochralski technique using resistive heating furnace and platinum crucible. We have optimized the growth parameters, after overcoming the problems encountered during the growth such as constitutional supercooling (CSC) and crystal cracking. Transmission spectra have been taken for the top, middle and bottom portions of the crystal and it is observed that transmission reduces towards the bottom portion of the crystal. The structure of the grown crystal was solved by direct methods with SIR97 program and refined by full matrix least squares with SHELX93. Single crystal X-ray diffraction data were collected at room temperature. (C) 2002 Elsevier Science B.V. All rights reserved.