This work deals with the design and implementation of an ECG interfacing system that is based on a personal computer using Industry Standard Architecture (ISA) bus. The system presented consists mainly of the hardware circuits and the operating system for software analysis. The hardware design deals with the selection and testing of appropriate required hardware components. It consists mainly of: electrodes, analog signal conditioning unit (input buffer amplifiers, lead selector network, instrumentation amplifier, filter circuits and second stage of amplification), analog-to-digital converter and the ISA bus. Similarly, the design of the operating system software, performs the task of identification of the ECG waveform. It consists of: design of the ECG interfacing card software (the ECG interfacing card program, configuration of the 8255A), signal conditioning, ECG waveform analysis and detection (QRS complex identification, P and T wave identification). The software of the system is implemented by using Quick Basic and Visual Basic languages. The main advantage of the system is to provide a reported ECG recording on a personal computer, so that it can be stored and processed at any time as required, and also it is useful to simulate the ECG signals of different types of ECG abnormalities which can be detected to do the required analysis algorithms on them. The proposed system is based on previous methods of data acquisition system which were improved on, to be used as an interfacing system of ECG monitoring and signal analysis.