Objective: This study aimed to assess the prevalence, the level of awareness, and the factors that increase hypertension in Turkey. Material and Methods: A cross-sectional survey with a multi-stage probability sampling was conducted. A total of 9604 people were screened; of them, 9316 had a complete clinical examination. The ages, genders, personal and family histories of hypertension, diabetes, coronary artery diseases were recorded. Their systolic and diastolic blood pressures (BP), heights, weights, waist, and hip circumferences were measured. Hypertension was defined as taking medication for hypertension or BP >= 140/90 mmHg. Results: According to the JNC-7 criteria, 22.1% of the population had prehypertension, 36.5% had hypertension (15.3% stage 1 and 21.2% stage 2 hypertension), and 41.4% were normal population. Of the population, 30% had an awareness of hypertension. The prevalence of hypertension was higher in Mediterranean, Central Anatolia, and Black Sea Regions and lower in South-East Anatolia, Aegean Regions, while it was similar in Marmara and East Anatolia Regions when compared to the general population of Turkey. Though rural life, advancing age, increasing body mass index, and waist to height ratio >0.5 were the factors responsible for an increased prevalence of hypertension, smoking was found to decrease the prevalence. Conclusion: The data of the SEMT hypertension study indicated that more than onethird of the adult population was hypertensive in Turkey. Furthermore, only one-third of the hypertensive adult population showed awareness of their hypertension.