Abstract： Objective To investigate the influence provided by irbesartan on aldosterone escape during an-giotensin-converting enzyme inhibitor(ACEI) therapy in patients with essential hypertension (EH). Methods 166 EH patients were treated with ACEI. Plasma angiotensin Ⅱ ( Ang Ⅱ ) and aldosterone(Ald) concentrations were meas-ured by radioimmunoassay following the therapy of 3 months treatment. Aldosterone escape was estimated by the plas-ma Ald level after 3 months treatment. Patients with aldosterone escape were given irbesartan for 6 months. The aldo-sterone escape were observed following the therapy with irebesartan at 1,3,6 months. Results Following the treat-ment of irbesartan for 1 month, plasma Ang Ⅱ and Ald concentrations significantly decreased (P < 0.01 ). However, it began to increase after 3 and 6 months treatment, still lower than that of the therapy not given irbesartan ( P < 0.01 ).The levels of plasma Ang Ⅱ and Aid were higher in 6 months than in 1,3 months ( P < 0.01 ), but there are no differ-ences between 1 and 3 months(P>0.05). Conclusion Irbesartan can reduce aldosterone escape during 6 months.But aldosterone escape may be occur again after 6 months treatment of irebesartan.