OBJECTIVES: To explore the efficacy of irbesartan in reducing blood pressure (BP) compared to candesartan, in a real-world setting. METHODS: We analysed the records of 10,338 (5,425 candesartan; 4,913 irbesartan) adult patients with hypertension who were initiated on the two agents between 1998 and 2006 using the UK THIN GP database. The analyses presented report the comparisons for General hypertensive patients (systolic BP (SBP) ≥ 140 mmHg, diastolic BP (DBP) ≥ 90 mmHg) and Severe hypertensive patients (SBP ≥ 180 mmHg, DBP ≥ 110 mmHg) on either ARB over the first 2 years of treatment. RESULTS: In the General hypertensive group mean SBP reductions at 1 year reached 14.7 mmHg for irbesartan vs. 13.6 mmHg for candesartan. Mean DBP reductions reached 8.5 mmHg for irbesartan and 7.1 mmHg for candesartan. In the Severe group, mean SBP reductions reached 31.6 mmHg for irbesartan vs. 31.2 mmHg for candesartan. Mean DBP reductions reached 15.8 mmHg for irbesartan vs. 13.4mmHg for candesartan. Similar comparisons were observed in the second year analysis. All but one of the comparisons were statistically significant in a multivariate analysis after adjusting for baseline BP, age, sex, weight, diabetes status, practice effect, socioeconomic status, 1st line vs. subsequent line usage, number of prior comorbidities, hypertensive diagnosis status and type of and number of co-therapies prescribed. In the General hypertensive population, patients receiving irbesartan showed a greater mean reduction in SBP of 1.18 mmHg (p<0.001) and of 0.55 mmHg (p<0.001) in DBP over 2 years compared to those receiving candesartan. Similar differences among therapies were observed in Severe patients, 1.79 mmHg in SBP (p=0.02), -0.10 mmHg in DBP (p=0.747). Significance may have been affected by the small number of patients in the Severe group. CONCLUSIONS: In a real-world setting, patients receiving irbesartan are observed to achieve greater BP reductions compared to those receiving candesartan.