The calcium antagonists of the dihydropyridine group, isradipine and nifedipine, were compared in 64 patients with mild to moderate hypertension (diastolic blood pressure 95 to 110mm Hg). A 2-week placebo run-in phase was followed by a double-blind crossover trial comprising two 3-week treatment periods with either calcium antagonist. The (fixed) dosages were isradipine 2.5mg twice daily and nifedipine retard 20mg twice daily. Blood pressure (systolic/diastolic) at baseline was 155/101mm Hg and decreased significantly by 14%/15% on isradipine and by 11%/12% on nifedipine (difference between treatments not significant). The drugs differed significantly with regard to incidence of adverse effects (mostly flushing and headache); the total rates were 16% on isradipine and 36% on nifedipine. At the end of the trial, patients were asked which drug or treatment phase they preferred. Isradipine was preferred by 50% of patients; only 20% preferred nifedipine. Thus, it is concluded that isradipine, administered in an equally effective antihypertensive dosage regimen is superior to nifedipine with regard to the incidence of adverse effects, resulting in greater patient satisfaction with treatment.