Résumé : A real time computerised dysrhythmia monitoring system which uses both a peripheral and a right intra atrial lead has been developed. The purpose of the intracardiac lead is to provide a strong P wave, thereby improving the quality of data available for analysis. The 2 leads are pre processed to produce electrical pulses representing auricular and ventricular activities, from which various time intervals are computed and analysed. Development of the analysis program was undertaken with the aid of a dysrhythmia data bank set up on magnetic tape (309 cases). Diagnosis of the basic rhythm was successful in 88% of the cases (389 out of 442 different basic rhythms). The detection of atrial premature beats (APB) was 80.2% successful (1,365 out of 1,752 APB), reaching 85.6% when the basic rhythm was regular and 62.5% when it was irregular. The detection of ventricular premature beats (VPB) was 88% successful (2,969 out of 3,051 VPB), reaching 90.3% when the basic rhythm was regular or irregular, and 69.2% in cases of atrial fibrillation. This monitoring system is now applied to CCU (coronary care unit) patients. Computer output appears in real time on displays located at the central station and at the patient's bedside. Information can be recorded on a hard copy unit. General information concerning the patients (4) appears on a table. Several graphs may be obtained; they show the evolution over any time period during the previous 24 hr of heart rate, PR interval, APB and VPB.