Holter monitoring is a technique which involves the use of a specialized recorder to record and analyze the ECG of an ambulatory subject for a duration up to 24 h. It is used for persons who have generally normal ECG, but who experience heart disorders under some particular stress conditions. This paper describes the design of an 8086-based Holter monitor using state-of-the-art technology. The old concept of analog signal processing and cassette recording has been replaced by digital signal processing and solid state memories. The main features of the new monitor, as compared with conventional ones, is its intelligence to detect and record arrhythmias which are of clinical importance. Emphasis was placed on miniaturization and minimization of the power consumption while designing the monitor.