The heart is the organ that pumps blood around the body. If the heart stops functioning, blood does not flow. The driving force for this flow is the pressure difference between the arterial blood leaving the heart and the returning venous blood. ‘Blood pressure and blood flow’ first considers how blood pressure is measured and how blood pressure can affect health. High blood pressure is called hypertension and low blood pressure hypotension. Chronic hypertension has serious long-term adverse health consequences, but can be treated with improved lifestyle choices and a range of medicines, including anti-hypertensive drugs, beta blockers, and ACE inhibitor drugs. The different molecules affecting blood flow are also considered.