The aim of this study was to evaluate ambulatory blood pressure monitoring in patients with essential hypertension and hypertension caused by adrenal pathology. Sixty-six patients with primary aldosteronism, 37 with pheochromocytomas, and 45 with adrenal incidentalomas were included. These patients were compared with 152 essential hypertensive patients and 64 normotensive subjects. Ambulatory blood pressure monitoring evaluated daytime and nighttime systolic and diastolic blood pressure and heart rate. The authors found that the "nondipper" phenomenon was present in 51.5% of patients with primary aldosteronism, 43.2% with pheochromocytomas, 42.2% with incidentalomas, 34.2% with hypertension, and 15% of subjects who were normotensive. In 58% of primary aldosteronism patients with idiopathic adrenal hyperplasia, there was an absence of the physiologic blood pressure nocturnal fall (nondipper), which was statistically significant (P<.001) compared with nondipper primary aldosteronism patients with adrenocortical adenoma (38%). In conclusion, the prevalence of the nondipping pattern was higher in patients with adrenal hypertension compared with patients with essential hypertension, suggesting an independent cardiovascular risk factor.