In briefECG monitoring is generally recommended for patients in cardiac rehabilitation, but the optimal amount of monitoring is uncertain. This article reviews several questions regarding this issue. The authors conclude that monitoring during exercise testing is necessary to determine an appropriate exercise prescription for all cardiac patients, but additional monitoring is not indicated during upper extremity as opposed to lower extremity exercise. They also believe that all patients entering exercise programs soon after hospital discharge should be monitored for at least seven weeks, and preferably 12. Periodic monitoring is useful for recognizing potential problems and evaluating long-term medication effectiveness.