OBJECTIVES: Lost Therapeutic Benefit (LTB) (receiving medication without attaining target BP levels) may lead to increased morbidity and mortality due to cardiovascular disease. Objectives of this study were to estimate the extent of LTB in patients at high risk of atherothrombotic events and to model the impact of attaining target BP levels in LTB patients on cardiovascular event rates over a two-year period METHODS: The Australian REACH registry consists of 2872 high-risk patients of which 2856 (99.4%) were followed for cardiovascular events over a two-year period.  The mean age was 72.8 ± 8.9 yrs, 65.1% were male and 78.7% had a history of hypertension. LTB was calculated as the proportion of patients receiving antihypertensive therapy who were not attaining guideline BP control targets. A hypothetical intervention to lower blood pressure to the normal range was applied to those individuals identified with LTB, to estimate the number of cardiovascular disease events which could be prevented.  Logistic regression was used to find the predictors of LTB and event rates were compared using Chi squared tests. RESULTS: Among the 2856 Australian REACH participants, 70.1% (n=2002) had uncontrolled blood pressure (>130/80 mmHg) and 88.3% (2522) had been taking anti-hypertensive medication.  LTB was 70.7% (1784).  The major univariate predictors of LTB were gender, age, diabetes, hypertension, carotid plaque, cholesterol, BMI and congestive heart failure.  Assuming a hypothetical blood pressure intervention is applied to the LTB group resulting in controlled blood pressure (≤130/80 mmHg), 8 cardiac events per 1000 people and 21 cardiovascular disease events including coronary heart disease intervention per 1000 people could be prevented. CONCLUSIONS: Improving BP control in patients receiving antihypertensive medication may prevent 8 cardiac events per 1000 people and 21 CVD events per 1000 people within this study group.  At a population level, this would represent a major cardiovascular event reduction strategy