Home blood pressure readings by self-monitoring (14 readings in 7 days) have been compared to readings taken in the clinic in 937 participants of the Tecumseh Blood Pressure Study. In the absence of firm criteria "hypertension at home" was defined as having home readings in the upper decile of the whole population. If a clinic reading exceeded 140 and/or 90 mmHg a subject was categorized as having clinic "hypertension". Two hypertensive groups emerged; one with both clinic and home hypertension ("sustained" N = 47) and one with high clinic but normal home blood pressure ("white coat" N = 50). Groups with "white coat" and "sustained" hypertension were very similar. Both groups were overweight, had faster heart rates, elevated cholesterol, insulin, triglyceride and decreased HDL levels. Blood pressure readings at previous exams (age 5, 8, 21 and 22) were elevated in both the "sustained" and white coat hypertension group compared to the normotensive controls. Subjects with white coat hypertension were not hyperresponders to the stress of mental arrythmetrics or to isometric exercise. The white coat hypertensives did not show abnormal anger, excessive submissiveness, or anxiety. The pathophysiology of the reproducible elevation of the clinic blood pressure in the white coat hypertensives remains unclear. Because of a higher risk of coronary heart disease and a risk for late development of sustained hypertension, subjects with white coat hypertension should be counselled on nonpharmacologic methods to control the blood pressure elevation and to ameliorate coronary risk factors.