The potential of polycrystalline silicon for large scale terrestrial photovoltaic device application is well recognized. It shares with single-crystal silicon numerous desirable physical and chemical properties, while also showing great promise of reduced cost by circumventing many of the complex and energy intensive steps associated with growth of single crystals. These facts have prompted many scientists to investigate various forms and shapes of polycrystalline silicon. The results involving SIS, MIS and p/n junction devices will be reviewed. Results will also be presented to show how grain boundaries play a dominant role in determining the electrical and photovoltaic properties of polycrystalline silicon.