OBJECTIVE: To determine the effectiveness of intensive structured care to optimise blood pressure control based on individual absolute risk targets in primary care. DESIGN: Pragmatic multicentre randomised controlled trial. SETTING: General practices throughout Australia, except Northern Territory, 2009-11. PARTICIPANTS: Of 2185 patients from 119 general practices who were eligible for drug treatment for hypertension according to national guidelines 416 (19.0%) achieved their individual blood pressure target during a 28 day run-in period of monotherapy. After exclusions, 1562 participants not at target blood pressure (systolic 150 (SD 17) mm Hg, diastolic 88 (SD 11) mm Hg) were randomised (1:2 ratio) to usual care (n=524) or the intervention (n=1038). INTERVENTION: Computer assisted clinical profiling and risk target setting (all participants) with intensified follow-up and stepwise drug titration (initial angiotensin receptor blocker monotherapy or two forms of combination therapy using angiotensin receptor blockers) for those randomised to the intervention. The control group received usual care. MAIN OUTCOME MEASURES: The primary outcome was individual blood pressure target achieved at 26 weeks. Secondary outcomes were change in mean sitting systolic and diastolic blood pressure, absolute risk for cardiovascular disease within five years based on the Framingham risk score, and proportion and rate of adverse events. RESULTS: On an intention to treat basis, there was an 8.8% absolute difference in individual blood pressure target achieved at 26 weeks in favour of the intervention group compared with usual care group (358/988 (36.2%) v 138/504 (27.4%)): adjusted relative risk 1.28 (95% confidence interval 1.10 to 1.49, P=0.0013). There was also a 9.5% absolute difference in favour of the intervention group for achieving the classic blood pressure target of ≤ 140/90 mm Hg (627/988 (63.5%) v 272/504 (54.0%)): adjusted relative risk 1.18 (1.07 to 1.29, P<0.001). The intervention group achieved a mean adjusted reduction in systolic blood pressure of 13.2 mm Hg (95% confidence interval -12.3 to -14.2 mm Hg) and diastolic blood pressure of 7.7 mm Hg (-7.1 to -8.3 mm Hg) v 10.1 mm Hg (-8.8 to 11.3 mm Hg) and 5.5 mm Hg (-4.7 to -6.2 mm Hg) in the usual care group (P<0.001). Among 1141 participants in whom five year absolute cardiovascular risk scores were calculated from baseline to the 26 week follow-up, the reduction in risk scores was greater in the intervention group than usual care group (14.7% (SD 9.3%) to 10.9% (SD 8.0%); difference -3.7% (SD 4.5%) and 15.0% (SD 10.1%) to 12.4% (SD 9.4%); -2.6% (SD 4.5%): adjusted mean difference -1.13% (95% confidence interval -0.69% to -1.63%; P<0.001). Owing to adverse events 82 (7.9%) participants in the intervention group and 10 (1.9%) in the usual care group had their drug treatment modified. CONCLUSIONS: In a primary care setting intensive structured care resulted in higher levels of blood pressure control, with clinically lower blood pressure and absolute risk of future cardiovascular events overall and with more people achieving their target blood pressure. An important gap in treatment remains though and applying intensive management and achieving currently advocated risk based blood pressure targets is challenging.