What is the difference between atenolol and lisinopril?

They are both antihypertensives or treatment for high blood pressure (and they have other uses as well) but their mechanism of action is a bit different. Atenolol is a beta blocker and lisinopril is an angiotensin converting enzyme inhibitor, otherwise known as an ACE inhibitor. While the mechanism through which lisinopril lowers blood pressure is believed to be primarily suppression of the renin-angiotensin-aldosterone system, atenolol inhibits beta2-adrenoreceptors, chiefly located in the bronchial and vascular musculature thus causing (1) reduction in resting and exercise heart rate and cardiac output, (2) reduction of systolic and diastolic blood pressure at rest and on exercise, (3) inhibition of isoproterenol induced tachycardia, and (4) reduction in reflex orthostatic tachycardia. So the differences are mainly in the mechanisms of their actions.