Resistant hypertension is an increasingly common problem faced by primary care physicians and specialists and will undoubtedly become even more common as the adult population ages and gains weight. In the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), at least 8% of subjects were resistant to treatment based on the need for three or more antihypertensive agents. Characteristics of patients with resistant hypertension include being older, black, obese, and diabetic, and having chronic kidney disease as well as untreated sleep apnea. Hyperaldosteronism is common in patients with resistant hypertension, with a prevalence of approximately 20%. This, however, is likely an underestimation of the role aldosterone excess plays in causing drug resistance. In subjects with resistant hypertension, suppressed renin levels are common, exceeding 75% in our studies, suggesting aldosterone excess effects beyond cases of true primary hyperaldosteronism. Recent studies indicate that aldosterone antagonists provide significant blood pressure reduction when added to antihypertensive regimens of patients with resistant hypertension. Interestingly, the blood pressure reduction with use of spironolactone is not limited to patients with hyperaldosteronism, consistent with the concept of aldosterone excess as a continuum from low-renin hypertension with normal aldosterone levels to true primary hyperaldosteronism.