PURPOSE: To compare the effectiveness on blood pressure (BP) of initial two-drug therapy versus monotherapy in hypertensive patients. METHODS: Using the Clinical Practice Research Datalink, linked with Hospital Episode Statistics and Office for National Statistics, we identified a cohort of adults with uncontrolled hypertension, initiating one or two antihypertensive drug classes between 2006 and 2014. New users of two drugs and monotherapy were matched 1:2 by propensity score. Main exposure was "as-treated," ie, until first regimen change. Primary and secondary endpoints were systolic and diastolic BP control and major adverse cardiovascular event (MACE), respectively. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazard models. RESULTS: Of 54 523 eligible patients, 3256 (6.0%) were initiated to a two-drug combination. Of these, 2807 were matched to 5614 monotherapy users. Mean exposure duration was 12.7 months, with 76.5% patients changing their initial regimen. Two-drug therapy was associated with a clinically significant BP control increase in all hypertensive patients (HR = 1.17 [95%CI: 1.09-1.26]), more so in patients with grade 2-3 hypertension (HR = 1.28 [1.17-1.41]). An increase of 27% in BP control (HR = 1.27 [1.08-1.49]) was observed in patients initiating an ACEi+CCB combination compared with initiators of either single class. No significant association was found between two-drug therapy and MACE. Several sensitivity analyses confirmed the main findings. CONCLUSIONS: Few patients initiated therapy with two drugs, reflecting UK guidelines' recommendation to start with monotherapy. This study supports the greater effectiveness of two-drug therapy as the initial regimen for BP control.