The use of digital scan converters in ultrasonic imaging is presented. The basic principles of ultrasound physics and imaging are briefly reviewed. A detailed description of the components and principles of operation of digital scan converters follows. The capabilities of current digital scan converters in terms of resolution, writing speed, pre-processing and postprocessing, and new rapid scanning techniques are discussed. A summary of the factors which limit performance demonstrates the interdependence of the ultrasonic pulse-repetition frequency, memory size and speed, magnification, depth of penetration, and the occurrence of Moire artifacts. Concluding remarks summarize the technology status and indicate expected future developments.