MICROELECTRONIC device integration has progressed to the point where complete ’systems-on-a-chip’ have been realized(1,3). Now that optoelectronics is becoming increasingly important for information and communication technologies, there is a need to develop optoelectronic devices that can be integrated with standard microelectronics, Conventional semiconductor technology is largely based on crystalline silicon, which (being an indirect bandgap semiconductor) is an inefficient light-emitting material. This has stimulated significant effort towards developing silicon-based optoelectronic components and, of the several strategies explored so far(4,5), the use of porous silicon appears the most promising; porous silicon produces high-efficiency, room-temperature, visible photoluminescence(6), and its material and optical properties have been studied in detail(7,8). But the extreme reactivity and fragility of porous silicon have hitherto prevented its integration with conventional silicon processing technology. We have recently shown(9,10) that the thermal and chemical stability of porous silicon can be greatly enhanced-while retaining desirable light-emitting and charge-transport properties-by partial oxidation. Here we take advantage of these improvements in material properties to demonstrate the successful integration of silicon-based visible light-emitting devices into a standard bipolar microelectronic circuit.