['According to the National Health survey only 3% of the population has controlled hypertension. This study was designed to elucidate the knowledge about hypertension in hypertensive patients at three tertiary care centers in Karachi. Secondly we sought to compare the knowledge of those with uncontrolled hypertension and controlled hypertension.', 'It was a cross-sectional study conducted at The Aga Khan University hospital (AKUH), Ziauddin Hospital (ZH) and Civil hospital, Karachi (CHK. All diagnosed Hypertensive patients (both inpatients and outpatients) coming to a tertiary care hospital in Pakistan aged > 18 years were included. Patients were categorized into 2 groups: controlled and uncontrolled hypertension based on their initial BP readings on presentation Uncontrolled Hypertension was defined as average BP ≥ 140/90 mm Hg in patients on treatment. Controlled Hypertension (HTN) was defined as average BP <140/90 mm Hg in patients on treatment. Standardized methods were used to record BP in the sitting position. Knowledge was recorded as a15 item question. Primary outcome was knowledge about hypertension.', 'A total of 650 participants were approached and consented 447 were found eligible. 284(63.5%) were from Aga Khan University, 101(22.6) from Dow University of health sciences and 62(13.9) were from Ziauddin University. Mean (SD) age of participants was 57.7(12) years, 50.1(224) were men. Controlled hypertension was present in 323(72.3) and uncontrolled hypertension was present in 124(27.4). The total mean (SD) Knowledge score was 20.97(4.93) out of a maximum score of 38. On comparison of questions related to knowledge between uncontrolled and controlled hypertension, there was statistically significant different in; meaning of hypertension (p <0.001), target SBP(p0.001), target DBP(p 0.001), importance of SBP versus DBP, improvement of health with lowering of blood pressure (p 0.002), high blood pressure being asymptomatic (p <0.001), changing lifestyle improves blood pressure(p 0.003),hypertension being a lifelong disease (<0.001), lifelong treatment with antihypertensives(<0.001) and high blood pressure being part of aging(<0.001). On comparison of knowledge as a composite score between uncontrolled and controlled hypertensive; Mean (SD) score was 21.85(4.74) v18.67 (4.70) (p value: < 0.001). On multivariate analysis; gender β (95% CI) 1.67(0.75, 2.59) p <0.001, uncontrolled blood pressure; -2.70(-3.76,-1.67) p <0.001, Sindhi ethnicity; -1.79(-3.25,-3.27) p 0.01 and pukhtoon ethnicity; -2.72(-4.13,-1.32) p <0.001 were significantly associated with knowledge score.'] Is good knowledge about hypertension linked to better control of hypertension ; a multicentre cross sectional study in Karachi , Pakistan?