White coat hypertension is considered to be a benign condition that does not require antihypertensive treatment. Ambulatory blood pressure (ABP) was measured in 284 participants in the Hypertension in the Very Elderly Trial (HYVET), a double-blind randomized trial of indapamide sustained release 1.5 mg±perindopril 2 to 4 mg versus matching placebo in hypertensive subjects (systolic blood pressure 160-199 mm Hg) aged >80 years. ABP recordings (Diasys Integra II) were obtained in 112 participants at baseline and 186 after an average follow-up of 13 months. At baseline, clinic blood pressure (CBP) exceeded the morning ABP by 32/10 mm Hg. Fifty percent of participants fulfilled the established criteria for white coat hypertension. The highest ABP readings were in the morning (average 140/80 mm Hg), the average night-time pressure was low at 124/72 mm Hg, and the average 24-hour blood pressure was 133/77 mm Hg. During follow-up, the systolic/diastolic blood pressure placebo-active differences averaged 6/5 mm Hg for morning ABP, 8/5 mm Hg for 24-hour ABP, and 13/5 mm Hg for CBP. The lowering of blood pressure over 24 hours supports the reduction in blood pressure with indapamide sustained release±perindopril as the explanation for the reduction in total mortality and cardiovascular events observed in the main HYVET study. Because we estimate that 50% had white coat hypertension in the main study, this condition may benefit from treatment in the very elderly.