The polysilanes (-SiRR'-) are a new class of semi-inorganic polymers with fascinating properties and considerable promise in a variety of applications. For example, some members of this series can be cast into transparent films, spun into fibers, and converted into silicon carbide at high temperatures. They can also be used as photoinitiators, resists in UV lithography, <i>p</i>-type semi-conductors when properly doped, and as reinforcing media in ceramics when converted in situ into beta-SiC fibers. -- AATA