This study was designed to investigate whether the L/N-type calcium channel blocker, cilnidipine, had a renoprotective effect compared with other calcium channel blockers. Twenty-five hypertensive patients with concomitant type 2 diabetes who had a urinary albumin-creatinine ratio (ACR) of 10 - 300 mg albumin/g creatinine and who had been treated with oral calcium channel blockers other than cilnidipine for more than 3 months were included. Patients' medication was changed to cilnidipine 10 mg/day or 20 mg/day without a washout period. Blood pressure and renal function were measured before and at 3 months after the new treatment. Heart rate was also determined as a marker for sympathetic nervous activity. After substitution of cilnidipine, blood pressure did not change significantly, but heart rate decreased significantly from 73.9 +/- 7.1 beats/min to 72.0 +/- 8.4 beats/min, and the log-transformed urinary ACR decreased to 82.9 +/- 49.4% of baseline values. The changes in urinary ACR and heart rate showed a significant positive correlation. Thus, there was a strong indication that cilnidipine may exert its renoprotective effect by inhibiting sympathetic nervous activity.