In brief: The need for expert supervision in cardiac rehabilitation exercise programs is generally accepted, but the use of ECG monitoring as a safety measure in such programs is controversial. No randomized controlled studies of monitoring vs supervision alone have been performed. Consequently, there is no uniform approach to the role of ECG monitoring in cardiac exercise programs. In addition, considerable expense for labor and equipment would be required to monitor all participants continuously for the duration of a program, which typically lasts 12 weeks. The data indicate that administrators of such a program would spend approximately $1 million on ECG monitoring over eight years in the hope of preventing one serious cardiac event.