Real-world adherence to pharmacotherapy cannot be studied in the confines of the traditional clinical trial. Thus, to better understand adherence to antihypertensive medication in actual practice, a literature search was conducted to identify observational database studies of the use of antihypertensive medication. Ten studies were identified: half studied adherence patterns after initial prescriptions to patients with a new diagnosis of hypertension, and the others evaluated antihypertensive medication use in a mix of patients with newly diagnosed or chronic hypertension. Overall, results demonstrated that adherence to treatment for hypertension in the first year is very poor. In addition, it appears that initial treatment with newer classes of drugs, such as angiotensin II antagonists, angiotensin converting enzyme inhibitors, and calcium channel blockers favors treatment adherence. This review also highlights and discusses possible under-lying factors contributing to these results and implications for physicians.