If hypertension in patients with diabetes mellitus type II is not adequately controlled by angiotensin-converting enzyme inhibitors (ACE-i), a beta-blocker is frequently added as second-line therapy. Recently, large randomized trials demonstrated the beneficial effect of second-generation dihydropyridine calcium-channel blockers in these patients. These compounds are increasingly being used to replace beta-blockers. Withdrawal of beta-blockers may influence diabetic control and may cause rebound hypertension. Any rebound hypertension from beta-blocker withdrawal may not occur if the beta-blocker is replaced with a calcium-channel blocker. A calcium-channel blocker will influence vascular resistance (VR) and blood pressure differently than a beta-blocker. Thirty-four patients with diabetes mellitus type II and a resting diastolic blood pressure above 90 mm Hg despite enalapril 10 mg daily (or equipotent dosages of other ACE-i) for at least 3 months were treated in an open label sequential comparison with the same ACE-i in combination with the beta-blocker metoprolol 100 mg for 3 months, and, subsequently for 3 more months with the same ACE-i in combination with the dihydropyridine calcium-channel blocker lercanidipine 10 mg once daily. After 6 weeks, patients with a diastolic blood pressure above 90 mm Hg were titrated up to 200 mg metoprolol or 20 mg lercanidipine once daily. Patients were examined every 6 weeks during the trial, and after 2 weeks while receiving lercanidipine. In addition to blood pressure measurements, VR was measured by iridium strain gauge plethysmography and expressed in units (1 unit = 1 mm Hg/mL blood/100 mL tissue per minute). Two of 34 patients did not complete the protocol because of non-compliance with the lercanidipine treatment in the first 2 weeks of treatment. Their data are included in the analysis. No rebound hypertension 14 days after the change-over of therapies was observed. (Mean arterial pressures [MAPs] were not significantly different from the point of withdrawal of the beta-blockers.) However, heart rate rose from 69+/-7 to 94+/-10 beats/min (p < 0.001). After 3 months on lercanidipine, MAP fell by 6+/-10 mm Hg (p = 0.002) compared to the point of withdrawal of the beta-blocker. Vascular resistance fell by 6.28+/-11.91 units (p<0.01), while glucosylated hemoglobin (HbA1c) rose by 0.4+/-0.5% (p<0.001) and body weight rose by 0.6+/-0.6 kg (p < 0.01). Multiple regression analysis revealed significant associations between decrease in VR, increase in HbAlc, and decrease in MAP, and partial dependence of these variables on one another. In hypertensive patients with diabetes type II, replacement of ACE-i and metoprolol with ACE-i and lercanidipine does not appreciably influence metabolic control and does not cause rebound hypertension. Lercanidipine was more effective than metoprolol as a second-line antihypertensive drug in these patients. At least two mechanisms may be involved: withdrawal of a pressor effect from the beta-blocker, and calcium-channel-mediated vasodilation.