In the present study, the influence of sodium ferulate (SF) on hypotensive effect and urinary excretion of TXB2 after captopril (CAP) was observed in 44 patients with essential hypertension. A single oral dose of CAP (50 mg) decreased mean arterial pressure (MAP) from 16.25 +/- 0.85 to 13.65 +/- 1.14 kPa, n = 28, (P less than 0.01), and increased urinary TXB2 excretion significantly from 119.12 +/- 57.12 to 183.32 +/- 78.61 pg/min, n = 16, (P less than 0.05). The administration of SF 300 mg/d for one day did not affect the MAP. CAP in combination with SF induced a decrease both in MAP from 16.33 +/- 1.14 to 13.83 +/- 1.77 kPa, n = 16, (P less than 0.01) and urinary TXB2 excretion from 155.89 +/- 69.64 to 133.43 +/- 60.01 pg/min, n = 16, (P greater than 0.05) though the latter was not so significant. Compared with the administration of CAP alone, the combination of CAP and SF induced stronger hypotensive effect (P less than 0.05) and the increased urinary TXB2 excretion could be inhibited by SF, but the inhibition to angiotensin converting enzyme was the same. These results suggested that the increased urinary TXB2 excretion by CAP can be inhibited and the hypotensive effect of CAP is potentiated by SF in essential hypertensive patients.