A multichannel microcomputer-based e.e.g. processing system is described. Using a unique method of digitisation, analogue-to-digital preprocessors perform period measurement and either peak-to-peak amplitude or absolute integral measurement on a wave-by-wave basis in real time. A scan circuit controls the high-speed transfer of preprocessor data over a shared data bus to a single-board microcomputer. The microcomputer tests for indications of artefact, sorts and accumulates the data by channel and wave category, and outputs the formated data on command or at regular intervals to external devices for storage, display, or further processing. The suitability of this type of processing system for the analysis of periodic and aperiodic components of the e.e.g. is discussed.