BACKGROUND: This study was designed to evaluate the antihypertensive efficacy and safety of nifedipine gastrointestinal system push-pull osmotic pump formulation in patients with mild to moderate essential hypertension. METHODS: After 2 weeks placebo run-in period, nifedipine 60 mg was administered once daily for 8 weeks in thirty-two patients with mild to moderate essential hypertension. RESULTS: At the end point of treatment, sitting blood pressure decreased as much as 33/16mmHg in average and rewarded 88% of efficacy and 69% of normalization. The ambulatoy blood pressure monitoring in 10 patients also revealed 11% decrease in 24 hr mean diastolic blood pressure and 32% decrease in % elevated blood pressure. The most frequent side reactions were constipation in 7 patients and polyuria in 6 patients which were tolerated during entire trial period. There were no significant changes in biochemical parameters and hematologic data, thus making the rate of safety 91% and overall rating of usefulness was 84%. CONCLUSION: Nifedipine GITS 60 mg once daily regimen is well tolerated and effective in the treatment of mild to moderate essential hypertension.