This study was aimed to describe the outcomes of a hypertension treatment programme in two outpatient clinics in Cambodia. We determined proportions of patients who met the optimal targets for blood pressure (BP) control and assessed the evolution of mean systolic and diastolic BP (SBP/DBP) over time. Multivariate analyses were used to identify predictors of BP decrease and risk factors for LTFU. A total of 2858 patients were enrolled between March 2002 and June 2008 of whom 69.2% were female, 30.5% were aged ≥64 years and 32.6% were diabetic. The median follow-up time was 600 days. By the end of 2008, 1642 (57.4%) were alive-in-care, 8 (0.3%) had died and 1208 (42.3%) were lost to follow-up. On admission, mean SBP and DBP were 162 and 94 mm Hg, respectively. Among the patients treated, a significant SBP reduction of 26.8 mm Hg (95% CI: 28.4-25.3) was observed at 6 months. Overall, 36.5% of patients reached the BP targets at 24 months. The number of young adults, non-overweight patients and non-diabetics reaching the BP targets was more. Older age (>64 years), uncontrolled DBP (≥90 mm Hg) on last consultation and coming late for the last consultation were associated with LTFU, whereas non-diabetic patients were 1.5 times more likely to default than diabetics (95% CI: 1.3-1.7). Although the definite magnitude of the BP decrease due to antihypertension medication over time cannot be assessed definitely without a control group, our results suggest that BP reduction can be obtained with essential hypertension treatment in a large-scale programme in a resource-limited setting.