Featuring papers from the 1991 MRS Spring Meeting (April 29 - May 3, Anaheim, California), this volume contains 93 papers presenting research in Si MBE, including a key paper from the special Late News session on light from porous silicon. Topics covered include: homoepitaxy and substrate preparation; doping; GeSi growth; GeSi optical properties; GeSi electronic transport; device applications; epitaxial metals and insulators; novel materials and growth techniques.