The objective of this study was to compare the safety and efficacy of nifedipine in two different formulations (osmotic pump and slow release microgranules) in patients with essential hypertension. A total of 91 patients with mild and moderate essential hypertension were recruited in a randomised, double-blinded trial, to receive a daily dose of 30 mg of nifedipine GITS or nifedipine slow release microgranules for 8 weeks. Patients who did not respond to the above-mentioned dose at week 4 of treatment received an increased dose of 60 mg per day of either drug for the remaining trial period. The primary end point of this study was the variation in mean sitting diastolic blood pressure (SDBP) from baseline values to the ones found at week 4 of treatment. The secondary end point was the variation in mean sitting systolic blood pressure (SSBP). Drug tolerability was measured according to incidence of side effects. The results were that both presentations reduced the mean SDBP and SSBP with similar efficacy. Drug side effects were also similar in both formulations. In conclusion nifedipine in slow release microgranules (NMG) is as effective as osmotic pump nifedipine (GITS) in reducing blood pressure with a similar tolerability profile.