Seventeen untreated and 36 treated hypertensives aged 65 years or more were referred to our clinic because of repeated values of systolic blood pressure > or = 160 mmHg and diastolic blood pressure > or = 95 mmHg. All 53 patients underwent 24h blood pressure monitoring during their customary daily activities. Eleven (65%) untreated and 23 (64%) treated patients were normotensive during their daily activities. Thus, ambulatory BP monitoring appears to be useful in the elderly hypertensive patients in detecting those whose BP is elevated only in the clinic. Ambulatory BP obtained outside the clinic may be useful in diagnostic and therapeutic decision-making in the elderly population.