In reply Sheps' comments are of interest. I am aware of his long-standing interest in ambulatory monitoring and of his efforts to standardize the procedure and define its usefulness in clinic practice. There is little doubt that at the Mayo Clinic (Rochester, Minn), where meticulous care is taken in patient instruction and application, fewer than 15% of the readings are unusable. But, in the real world of practice, a greater number of recordings are not interpretable.
Ambulatory monitoring is useful in research and in the evaluation of newer drugs. Even if there were no problems with the recordings, however, the data generated would probably be of little value in defining who should or should not be treated in the majority of cases. If casual blood pressure readings remain elevated to levels of 140/90 mm Hg or higher, the patient should be treated regardless of whether or not the ambulatory blood