Patients with resistant hypertension are at risk for poor outcomes. Medication adherence and intensification improve blood pressure (BP) control; however, little is known about these processes or their association with outcomes in resistant hypertension. This retrospective study included patients from 2002 to 2006 with incident hypertension from 2 health systems who developed resistant hypertension or uncontrolled BP despite adherence to >/=3 antihypertensive medications. Patterns of hypertension treatment, medication adherence (percentage of days covered), and treatment intensification (increase in medication class or dose) were described in the year after resistant hypertension identification. Then, the association between medication adherence and intensification with 1-year BP control was assessed controlling for patient characteristics. Of the 3550 patients with resistant hypertension, 49% were male, and mean age was 60 years. One year after resistance hypertension determination, fewer patients were taking diuretics (77.7% versus 92.2%; P<0.01), beta-blockers (71.2% versus 79.4%; P<0.01), and angiotensinogen-converting enzyme inhibitor/angiotensin receptor blocker (64.8% versus 70.1%; P<0.01) compared with baseline. Rates of BP control improved over 1 year (22% versus 55%; P<0.01). During this year, adherence was not associated with 1-year BP control (adjusted odds ratio, 1.18 [95% CI: 0.94-1.47]). Treatment was intensified in 21.6% of visits with elevated BP. Increasing treatment intensity was associated with 1-year BP control (adjusted odds ratio, 1.64 [95% CI, 1.58-1.71]). In this cohort of patients with resistant hypertension, treatment intensification but not medication adherence was significantly associated with 1-year BP control. These findings highlight the need to investigate why patients with uncontrolled BP do not receive treatment intensification.