The short and long term hypotensive effects of oral administration of bepridil were investigated in 26 patients with essential hypertension. A new calcium antagonist, bepridil inhibits the ion influx through sodium and potassium channels as well as calcium channels by directly affecting these channels. The drug (150 mg) rapidly decreased blood pressure (BP) from 157 +/- 12/97 +/- 8 to 137 +/- 10/86 +/- 8 mmHg (mean +/- SD, p less than 0.01) and heart rate (HR) from 64 +/- 5 to 58 +/- 4 beats/min (p less than 0.01) (n = 6) in 2 hours. Long term administration of 150 mg bepridil daily (50 mg t.d.s.) decreased BP from 169 +/- 6/104 +/- 8 to 143 +/- 14/83 +/- 7 mmHg (p less than 0.001), but did not change HR (66 +/- 4 and 67 +/- 5 beats/min, before and after administration) (n = 9). Bepridil at 300 mg (100 mg t.d.s.) decreased BP from 172 +/- 15/105 +/- 8 to 146 +/- 11/88 +/- 4 mmHg (p less than 0.001) and HR from 76 +/- 11 to 70 +/- 8 beats/min (p less than 0.01) (n = 9). No side effects were observed. In conclusion, the hypotensive and negative chronotropic actions of bepridil are beneficial in the short and long term treatment of essential hypertension.