Despite improvements in the management of hypertension in the past several years and the numerous efficacious antihypertensive agents available to today's physician, nearly 70% of patients do not have their hypertension adequately controlled. Noncompliance with prescribed regimens appears to be one of the primary contributors to the large numbers of patients with uncontrolled hypertension. A behaviour that can affect all patients, noncompliance is perplexing because it remains largely unrecognized in clinical practice. Several types of noncompliance exist, the 'drug holiday' being the most common. Good communication with the patient and the entire health care team is essential to improving patient compliance. Long-acting medications that provide good control of blood pressure beyond the 24 h dosing period should be considered as the drugs of choice in noncompliant hypertensive patients. This article discusses different types of compliance, methods of measuring compliance, and the clinical consequences of noncompliance in hypertension.