We studied differences in the effects of a long-acting angiotensin-converting enzyme (ACE) inhibitor (temocapril) and a long-acting calcium channel blocker (amlodipine) on ventricular ectopic beats (VEB) in relation to sympathetic nerve activity in 46 patients with essential hypertension. We performed 24-h Holter electrocardiography and ambulatory blood pressure (BP) monitoring simultaneously, and examined blood samples during the baseline, temocapril and amlodipine treatment periods. The ambulatory BP was lower in the amlodipine period than in the temocapril period. However, the number of VEB was significantly increased in the amlodipine period compared to that in the baseline period (11.9 vs. 7.4/day, p<0.05). In the temocapril period, the number of VEB was not significantly increased compared to that in the baseline period (8.6 vs. 7.4/day, p=0.30). Ambulatory heart rate (HR) was significantly increased in the amlodipine period compared to that in the baseline period (24-h HR: 70 vs. 66 bpm, p<0.001; daytime HR: 75 vs. 71 bpm, p<0.001; nocturnal HR: 60 vs. 58 bpm, p<0.05). Plasma norepinephrine (NE) also was significantly increased in the amlodipine period compared to that in the baseline period (457 vs. 369 pg/ml, p<0.001). However, when patients receiving amlodipine were divided into a high dose group (8.6 +/- 1.2 mg/day) and a low dose group (4.6 +/- 1.2 mg/day), increases in HR and plasma NE levels were found only in the high dose group. These results indicate that amlodipine is effective at lowering BP in older hypertensives, although it may increase VEB, especially when given at a high dose.