Objective: The May Measurement Month (MMM) initiative is an annual global screening and awareness campaign started in 2017 by the International Society of Hypertension highlighting the importance of regular measurements of blood pressure (BP), the most important modifiable risk factor contributing to cardiovascular and all-cause mortality worldwide. Here we report on the results of the MMM campaign done in Belgium during the month of May in 2017, 2018, 2019, 2022 and 2023. Design and method: Participants 18 years or older were recruited through opportunistic sampling in 12 sites (mostly hospital entrances) across Belgium. Apart from standardized BP recordings (OMRON automated devices) by trained staff, data were collected on demographics, lifestyle factors and comorbidities. Hypertension was defined as raised blood pressure (systolic BP =>140 mmHg and/or diastolic BP => 90 mmHg) and/or taking antihypertensive medication. Age-standardized prevalence rates were calculated using the overall Belgian population (1st Jan 2023) as reference. Results: Data were collected from 5,926 participants aged 51.5 years on average. Mean (SD) systolic and diastolic blood pressures were 125.9 (17.6) mmHg and 79.4 (10.9) mmHg with 26.7% exceeding the 140/90 mmHg threshold. Age-standardized prevalences (95% CI) of hypertension were 45.4% (42.6%-48.1%) in men and 36.9% (34.8%-39.0%) in women. Among the 2,468 individuals with hypertension, 1,938 (78.5%) had been previously diagnosed and 1,578 (81.4%) of those with known hypertension, received antihypertensive treatment. Only about half of those being treated (56.3%) did achieve the target of systolic/diastolic BP <140/90 mmHg. Inadequate therapeutic control was independently associated with increasing age and higher body mass index. Untreated hypertension was significantly associated with male sex, age, body mass index and alcohol use. Conclusions: Despite the potential limited representativeness of the sample, these data suggest that the ‘rule of halves’ for hypertension does not longer hold in Belgium and that therapeutic control of hypertension is still suboptimal.