Background : Candesartan is a long-acting. selective angiotensin II type 1 receptor blocker. It is administered orally as the inactive prodrug candesartan cilexetil (CC) which is rapidly and completely converted to candesartan during gastrointestinal absorption. The objective of this study was to confirm antihypertensive efficacy and safety of CC through comparing with enalapril maleate (EM) in mild to moderate essential hypertensive patients. Methods : This study was an two centers, randomized, rouble-blind, non-inferiority study of once-daily 8mg CC versus 10mng EM, including 78 (age, 32 to 72 years) mild to moderate essential hypertensives (mean sitting diastolic blood pressure (MSiDBP), $95{sim}114mmHg$) for 8weeks. After 4 weeks study period, drugs were eventually increased to 16mg and 20mg in non-responders who were defined as MSiDBP was equal to or greater than 90mmHg. The reduction of trough MSiDBP, side effects and laboratory findings were compared between CC and EM at the end of this study. Results : In the 66 patients evaluable for intention to treat analysis, at the end of 8 weeks of treatment, reduction of MSiDBP were similar in both drugs ($14.4{pm}7.7mmHg$ for CC, $10.2{pm}9.8mmHg$ for EM, p=0.059). There was no significant difference between the two drugs in the systolic blood pressure reduction, blood pressure normalizing rate, number of rose escalation patients. Cough significantly less occurred in CC group but other safety profiles were comparable in both groups. Conclusion: The antihypertensive efficacy, safety and tolerability of once-daily administration of CC are not inferior to those of EM in essential hypertensive patients.