A short-term trial of isradipine was conducted to assess its effectiveness and tolerability in the treatment of mild-to-moderate hypertension. The study was carried out by general practitioners and involved 2,702 patients, aged 18-70 years, who had diastolic blood pressures (DBP) of 95-114 mm Hg. Patients completed a pretreatment phase of up to 4 weeks for antihypertensive drug washout and placebo run-in, before entering a 12-week active-treatment phase with 1.25 mg of isradipine twice daily, which was increased after 4 weeks to 2.5 mg twice daily, depending on the blood pressure response. At the end of 12 weeks, the mean systolic blood pressure (SBP) and DBP were 148.1 and 86.7 mm Hg compared with 169.0 and 103.0 mm Hg after placebo, respectively. The majority of patients (89.6%) had a DBP reduction greater than 10 mm Hg, and 86.2% had normalized DBP (less than or equal to 90 mm Hg) at the end of treatment. Adverse events were reported by 2.8% of patients, and 90% of patients and general practitioners reported satisfaction with the treatment. Thus, our results indicate that isradipine is effective and well tolerated, and may deserve a place as first-line treatment in mild-to-moderate hypertension.