The authors relate their own experience with 24 hr Holter monitoring in course of cardiac rehabilitation after coronary bypass surgery as well as after valvular replacement. As regards patients after coronary surgery they report the experience they got in the evaluation of heart rate trend and cardiac arrhythmias as well as in silent ischemia study. About this last problem 116 patients with signs of ischemia both in stress test and in Holter recording are considered out of 491 who had undergone coronary surgery. Ischemia during 24 hr Holter monitoring develops at an heart rate lower than effort ischemia. Holter monitoring proves to be very useful also in patients after valvular replacement to study arrhythmias and to check drugs' efficacy. After displaying the results concerning arrhythmias of 24 hr Holter electrocardiograms recorded in 207 randomized patients who had undergone valvular replacement 15 days before, the authors dwell upon the use of Holter electrocardiography in 82 valvular patients after pharmacological cardioversion and show that major arrhythmias get a clear reduction thanks to rehabilitation.