Purpose of review Refractory hypertension is a recently proposed phenotype of antihypertensive treatment failure. As such it represents an extreme subtype of resistant or difficult-to-treat hypertension. Resistant hypertension is relatively common with an estimated prevalence of 10-20% of treated hypertensive patients. It is typically defined as having an uncontrolled blood pressure on three or more antihypertensive medications, including a diuretic. Refractory hypertension is rare with a prevalence of approximately 5% of patients with uncontrolled resistant hypertension. It is defined as an uncontrolled blood pressure with the use of five or more antihypertensive medications, including a long-acting thiazide diuretic, such as chlorthalidone, and a mineralocorticoid receptor antagonist such as spironolactone. Recent findings Persistent excess fluid retention is thought to commonly underlie development of resistant hypertension, recent studies suggest that refractory may be more likely attributable to heightened sympathetic output as opposed to inappropriate fluid retention. Summary Treatment recommendations for resistant hypertension are generally based on intensification of diuretic therapy, especially with combined use of chlorthalidone and spironolactone. Although fuller elucidation is needed, such an approach may not be appropriate for refractory hypertension, which instead, may require effective sympathetic inhibition, either with medications or device-based approaches.