Abstract: Objective: To observe aldosterone escape in the therapy of essential hypertension with different RAS inhibitors.Method: One hundred and twenty-three patients with essential hypertension were randomly assigned to receive valsartan (80mg/d, n=61) or benazepril (10mg/d, n=62).The blood pressure, plasma PRA, AngⅡ, Ald levels were determined at the following time points:before treatment and first month, third month, sixth month after therapy.Result: ①The levels of blood pressure decreased in both groups, and no significant difference was found between them (P＞0.05).②In benazepril group, the plasma PRA remained unchanged before and after therapy.After therapy for one month, the AngⅡ level was significantly lower than that before treatment (P＜0.05).However, after therapy for 3month and 6month, the AngⅡ level gradually increased to baseline level, without significant difference comparing with that before therapy (P＞0.05).The Ald concentration notably decreased (P＜0.01) after one-month treatment, however it increased after three-months therapy, without difference from that before therapy (P＞0.05).There was significantly higher Ald level after six-month treatment than baseline level (P＜0.01).Aldosterone escape was observed in 24 patients and the incidence was 39%.③In valsartan group, there was also no difference (P＞0.05) between the PRA of baseline and that of one-month, three-month, six-month therapy.Compare with the baseline level, the concentration of AngⅡ slightly increased after one-month andthree-month treatment without statistical significance (P＞0.05), but the concentration significantly increased after six-month therapy than that of baseline (P＜0.05).After one-month treatment, the plasma Ald visibly falled compared with the baseline (P ＜ 0.05).It continued falling after three-month therapy, however, it increased slightly after six-month therapy butstill lower than that of baseline (P＜0.05).Conclusion: Aldosterone escape may be observed in some patients with essential hypertension when the treatment with ACEI last more than three months.To some degree, There is aldosterone escape during ARB treatment, however, the degree of escape is slighter and the time of beginning to escape is later than that during ACEI therapy.