Background & Objectives: Hypertension is one of the most important and common health problems in societies. Hypertension is often asymptomatic and can be simply treated. Many of drugs are available for treatment of hypertension i ncluding d iuretics, beta blockers, blockers of calcium channel, angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, alpha blockers and arterial dilators. This research was performed to evaluate the efficacy of some of these drugs on the hypertension. This may help to choose an appropriate medication for the treatment of stage 2 hypertension.

  Methods: A total of 150 patients with hypertension who were not under antihypertensive treatment and didn’t have contraindications for using hydrochlorothiazide , enalapril and atenolol were randomly allocated into three groups. These groups received atenolol 50 mg daily, hydrochlorothiazide 50 mg daily and enalapril 5 mg twice daily, respectively . After three weeks blood pressure of patients was measured and results were analyzed using SPSS.

  Results: Atenolol reduced systolic blood pressure (26.7±6.7 mm Hg 16.1%), diastolic blood pressure (10.3±1.2 mm Hg 10.4%) and mean arterial blood pressure (16.1±6.4 mm Hg 13.1%). Enalapril reduced systolic blood pressure (30.6±8.8 mm Hg 17.4%), diastolic blood pressure (11.5±4.4 mm Hg 11.4%) and mean arterial blood pressure (17.9±7.0 mm Hg 14.2%). Hydrochlorothiazide reduced systolic blood pressure (25.1±5.8 mm Hg 14.6%), diastolic blood pressure (9.2±2.3 mm Hg 9.3%) and mean arterial blood pressure (14.5±6.4 mm Hg 11.8%).

  Conclusion: Despite recommendations the use of hydrochlorothiazidein the treatment of hypertension, seems lower effect only use of this drug groups in comparison with other groups, and maybe add this category to other drugs and combined treatment is better than monotherapy with these groups .