The cost of commercial electron beam lithographic (EBL) systems can be prohibitive for institutions with limited resources who wish to fabricate short gate transistors or circuits requiring high resolution processing. This paper describes an EBL system, based on a modified scanning electron microscope which is inexpensive to construct yet can satisfy the high resolution lithographic requirements of many research centres. The system can handle standard data from a CAD system by writing the overall pattern as an array of stitched fields using metal registration marks. The field size is 400 μm square with a pixel size of 0.1μm. The overall array size is limited to 20mm square. To date the system has been used to fabricate monolithic amplifiers incorporating dual 200 μm wide MESFETS with 0.5 μm long gates and a process test pattern. The system is implemented using microprocessor based hardware linked to a host computer. Beam control, stage movement and wafer imaging are controlled by the microprocessor. Pattern generation and data manipulation are performed on the host computer.