Silicon bipolar device technologies provided 65% of the world's integrated circuits in 1983. Where low noise, high current, low or high voltage, high speed or low cost are required, bipolar technologies are used. This paper will review the present status of bipolar device technologies, which make possible 100-ps gate-propagation delays, 150-μm 2 gate areas, 1-GHz bandwidth amplifiers, on-chip control of over 1-A, 350-V operation, 14-GHz f T 's and 10-ns. analogue-to-8-bit digital conversion. These devices are realized because of advances in isolation techniques, chemical-vapor deposition, photolithography, diffusion, ion implantation, conductor–contact interconnection technology, etching processes, and materials preparation. This paper will discuss some of the fundamental problems, modelling difficulties, and technological barriers that will impact the future development of bipolar integrated circuits.