Patients’ persistence with chronic treatment is a major component in the effectiveness assessment. OBJECTIVE: To evaluate whether the initial choice of antihypertensive agent impacts newly diagnosed hypertensive patients’ persistence with treatment at one year. METHODS: The comparisons were between patients initially prescribed irbesartan, angiotensin II receptor antagonists (AIIRA) versus other antihypertensive drugs. We compared the proportion of patients who remained on the monotherapy initially prescribed, added to their initial therapy, switched to another therapy, or discontinued therapy at one year using chi-squared tests. Monotherapy duration was analyzed using the Kaplan Meier estimates. Statistical comparison of the survival curves was done with the Log-rank test. We pooled IMS Mediplus data (patient medical records completed by general practitioners) from Germany, France and the United Kingdom for analysis. Data was obtained for all irbesartan patients with at least one year of follow up and from randomly selected samples of patients treated with either diuretics, beta-blockers, calcium channel blockers, ACE inhibitors, or other AIIRA. Patients were newly diagnosed with hypertension between October 1, 1997 and November 30, 1998 and initiated antihypertensive treatment as monotherapy. RESULTS: Patients included (2,416) were initiated on diuretics (422), beta blockers (441), calcium channel blockers (466), ACE inhibitors (333), losartan (188), irbesartan (380), other AIIRA (186). When irbesartan was prescribed, more patients remained on that therapy (60.8%) than with all other antihypertensives (44.2% p=0.001), or other AIIRAs (51.3% p=0.009). Compared to patients taking all other antihypertensives, fewer patients receiving Irbesartan required adjunctive therapy (16.1% vs 25.3% p=0.001) or switched therapy (9.0% vs 13.6% p=0.013) CONCLUSIONS: Irbesartan was superior compared to all antihypertensives in achieving persistence of initial therapy. By evaluating persistence rather than compliance, we captured both the patient’s and the physician’s role in determining the course of treatment.