Office blood pressures were compared with those obtained using a thirty minute recording with an automatic device (Dinamap) in thirty patients with essential hypertension and nineteen subjects with hypertension and renal artery stenosis. When matched for age and sex, no differences were found between both groups of patients with respect to their office or automatically recorded blood pressures. The difference between office and automatically assessed systolic blood pressures was similar in both groups. The difference in diastolic pressures was slightly larger in the group with renal artery stenosis. The number of patients showing a pressure drop greater than 10 mm Hg was comparable in the two groups. We conclude that blood pressure levels obtained in the office overestimate 'true' blood pressure not only in essential but also in renovascular hypertension.