Flies are capable of rapidly detecting and integrating visual motion in(cid:173) formation in behaviorly-relevant ways. The first stage of visual motion processing in flies is a retinotopic array of functional units known as el(cid:173) ementary motion detectors (EMDs). Several decades ago, Reichardt and colleagues developed a correlation-based model of motion detection that described the behavior of these neural circuits. We have implemented a variant of this model in a 2.0-JLm analog CMOS VLSI process. The re(cid:173) sult is a low-power, continuous-time analog circuit with integrated pho(cid:173) toreceptors that responds to motion in real time.