The development of semiconductor nanowires has recently been the focus Of extensive research as these structures may play an important role ill the next generation of: nanoscale devices. Using semiconductor nanowires as building blocks. a number of high performance electronic devices have been fabricated. In this review. we discuss synthetic methodologies and electrical characteristics of Si, Ge, and Ge/Si core/shell nanowires. In particular the fabrication and electrical properties of a variety of nanowire-based field effect transistors (FETs) are discussed. Although the bottom-up approach has the potential to go far beyond the limits of top-down technology, new techniques need to be developed to realize precise control of structural parameters, such as size uniformity, growth direction, and dopant distribution within nanowires to produce nanowire-based electronics on a large scale.