The technique of automated whole-day blood pressure monitoring by noninvasive, lightweight portable devices has recently become available for clinical use. This article, together with the six that follow it, comprise the proceedings of a symposium on the diagnostic and prognostic use of this new approach. There is a growing belief that standard clinical methods may overdiagnose hypertension (the phenomenon of "white coat" or "office" hypertension), subjecting some patients to unnecessary long-term treatment. The automated blood pressure monitoring procedure may be especially helpful in evaluating patients whose office-diagnosed hypertension is not associated with confirmatory clinical findings or history. Data derived from whole-day blood pressure measurements appear to be more reproducible than conventional blood pressure values and correlate more closely with evidence for cardiovascular changes. This symposium has addressed some of the issues associated with the monitoring techniques, including the accuracy of values obtained with noninvasive equipment, interpretation of the data, and costs of the procedure. The evidence and arguments presented by these papers suggest that automated blood pressure monitoring is becoming a justified and desirable procedure in selected patients with a preliminary clinical diagnosis of mild to moderate hypertension.