OBJECTIVE : β-Blocker use has been controversial for a long time in the management of hypertensive patients with obstructive sleep apnea (OSA). The aim of present study was to compare the effects of metoprolol on BP lowering with amlodipine in hypertensive OSA patients. METHODS : Hypertensive subjects with OSA were randomly assigned to metoprolol and amlodipine groups, receiving 12 weeks of oral either metoprolol (47.5 mg once daily) or amlodipine (5 mg once daily) treatment. At baseline and after the 12-week treatment period, 24-h ambulatory blood pressure monitoring was performed in both groups. RESULTS : Both of metoprolol and amlodipine treatments significantly lowered 24-h blood pressure (BP) (from 143/88 to 132.3/81.6 mmHg; from 141.3/84.5 to 133.7/80.8 mmHg), daytime BP (from 146/90.2 to 136.4/84.6 mmHg; from 145.1/87.6 to 138.2/84.1 mmHg), and nighttime BP (from 139.1/83.9 to 125.7/76.2 mmHg; from 134.5/78.5 to 125.8/74.1 mmHg) (all P < 0.05). But there were no significant differences between the groups in BP variability (P > 0.05). Besides, metoprolol significantly reduced daytime heart rate (HR) (P < 0.05), while 24-h and nighttime HR values had no remarkable changes compared with baseline (P > 0.05). CONCLUSIONS : Metoprolol had similar therapeutic effects on BP lowering as amlodipine and could not decrease HR during the nighttime in hypertensive patients with OSA.