A multicentre, randomised, double-blind, parallel group comparison of nifedipine GITS 20 mg (Adalat LA) once daily and bendrofluazide 2.5 mg once daily in patients with mild-to-moderate hypertension was conducted. Two hundred patients with a diastolic blood pressure (BP) in the range 95 to 109 mm Hg were randomised to active treatment for 6 weeks. For the per-protocol efficacy population, both treatments resulted in clinically significant mean reductions of trough diastolic BP (nifedipine GITS -8.9 mm Hg, bendrofluazide -7.9 mm Hg) and systolic BP (nifedipine GITS -10.4 mm Hg, bendrofluazide -10.5 mm Hg). The study demonstrated that nifedipine GITS was 'at least equivalent' to bendrofluazide in the reduction of trough diastolic BP (one-sided upper 95% confidence limit, 0.5 mm Hg), where inequivalence had been pre-defined as a difference in mean diastolic BP of > or =5 mm Hg. Both drugs were well tolerated, the overall incidence of adverse events in the nifedipine GITS treatment group being 34.0% (34/100) and in the bendrofluazide treatment group being 29.0% (29/100). The commonest events (incidence > or =5%) were headache, constipation, 'flu syndrome and vasodilatation with nifedipine GITS and headache and nausea with bendrofluazide. An increased incidence of elevations of plasma urea and glucose was observed in patients treated with bendrofluazide (9.6% and 30.4% respectively) compared to those treated with nifedipine GITS (3.1% and 18.8% respectively). Nifedipine GITS 20 mg once daily is 'at least equivalent' to bendrofluazide 2.5 mg once daily in reduction of blood pressure in patients with mild-to-moderate hypertension.