Cardiovascular events are frequently reported in patients with acromegaly and they are usually related to arterial hypertension. Aim of the present study was to assess the 24-hour profile of blood pressure (BP) and heart rate (HR) in patients with active acromegaly and to correlate them with clinical and hormonal data. Sixteen patients and 16 healthy, age and sex matched subjects underwent ambulatory blood pressure monitoring by means of a portable automatic device (SpaceLabs monitor 90207, Kontron) with measurements every 20 minutes for 24 hours. The presence of the nocturnal fall was assessed by the calculation of the night-day systolic and diastolic ratio. The mean 24-hour diastolic BP was significantly higher in acromegalic patients than in controls (79.1+/-11.5 mmHg vs 70.8+/-5.3 mmHg, p<0.05) and the circadian diastolic profile was flatten. In fact, 10/16 patients were defined as nondippers while this figure was 2/16 in the control group (62% vs 12%, p<0.01). Also the mean 24-hour systolic BP was higher in acromegalic patients than in controls (124.8+/-17.2 mmHg vs 114.1+/-8.6 mmHg, p<0.05). The circadian systolic profile paralleled that of diastolic and was flatten, without a significant nocturnal fall. Ten out of 16 patients were nondippers compared to 2/16 controls (62 vs 12%, p<0.01). No significant correlation was found between mean 24-hour BP, either diastolic or systolic, and demographic or hormonal characteristics of the patients. HR patterns did not differ between patients and controls and were characterized by a prominent nocturnal fall.