This article reviews recent advances in research of helical conformations of optically active polysilylenes in solution. The helical conformation induces strong circular dichroism, chain stiffness, and liquid crystallinity in polysilylene chains, and it sensitively affects electronic state in the Q-conjugated silicon backbone. The helical conformation is determined by the internal rotation potential of the silicon backbone, and it turns out that the internal potential remarkably depends on the chemical structure of side-chains bonded to polysilylenes. Interrelations among these properties, the internal potential, and the side-chain chemical structure are discussed for optically active poly(dialkylsilylene)s. (C) 2003 Elsevier Ltd. All rights reserved.