Changes in blood pressure (BP) and pulse rate were measured during visits to a doctor's office by means of an non-invasive ambulatory BP monitoring device in 47 elderly hypertensive patients (mean age 73.0 years). Systolic BP increased from 140.5/85.4 mmHg to 157.9/85.7 mmHg immediately after entering the doctor's office and tended to return to the previous level at 5 minutes after entering although diastolic BP did not change during the visit. Pulse rate also increased slightly, but significantly on entering the office. The difference in BP between 25 minute before and just after entering an office was +17.4 mmHg in systolic. -0.1 mmHg in diastolic. If an increment in systolic BP more than 10 mmHg was defined as positive for white coat effect, they were observed in 59.6%. The frequency of white coat hypertension was 46.7% in the age of sixties, 65.2% in seventies and 66.7% in eighties but there was no significant difference among 3 groups. There was a tendency for white coat hypertensions to be more frequent in men compared than in women (p = 0.07).