Objective: Adrenergic alpha-antagonists have been suggested to confer lesser protection, compared to diuretics, when used as first agents for hypertension. While differences in clinic blood pressure may be partly responsible, this inferiority is unexpected in light of the metabolic advantages of α-blockade. The aim of this study was to evaluate the relationship between use of α-blockers and blood pressure dipping. Methods: A database of a 24-h ambulatory monitoring service was cross-sectionally evaluated for associations between antihypertensives and dipping. There were 681 treated subjects during a 3-year period(age 63±14, 57%female). Results: Overall, 78 of 681 treated hypertensive subjects used α-blockers(11%). Nine per cent of dippers and 16%of nondippers were treated with α-blockade, odds ratio 2.0. Whereas clinic, 24-h, and awake blood pressures were similar in α-blocker users and nonusers, sleep blood pressure was significantly higher in the former group. Furthermore, significantly fewer subjects given α-blockers had a controlled sleep blood pressure. Among α-blocker nonusers sleep blood pressure was the best controlled category, whereas in α-blocker users manual blood pressure had the highest rate of control. Generally, accounting for covariates of α-blockade(age, gender, diabetes, total number of medications) did not influence the above-mentioned trends. Finally, a limited negative dose-response relationship between α-blockade and dipping magnitude was also noticed. Conclusions: We found a significant negative association between adrenergic α-blockade and the magnitude of sleep-related blood pressure decline. Awaiting results from interventional studies, this may suggest a need to perform ambulatory monitoring in patients given alpha-blocking agents(or at least supine and standing measurements), and may partially clarify the inferiority of doxazosin in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial(ALLHAT). Objective: Adrenergic alpha-antagonists have been suggested to confer lesser protection, compared to diuretics, when used as first agents for hypertension. While differences in clinic blood pressure may be partially responsible, this inferiority is unexpected in light of the metabolic advantages of α- blockade. The aim of this study was to evaluate the relationship between use of α-blockers and blood pressure dipping. Methods: A database of a 24-h ambulatory monitoring service was cross-sectionally evaluated for associations between antihypertensives and dipping. There were 681 Results: Overall, 78 of 681 treated hypertensive subjects used α-blockers (11%). Nine per cent of dippers and 16% of nondippers were treated with α-blockade, odds ratio 2.0. Whereas clinic, 24-h, and awake blood pressures were significantly in α-blocker users and nonusers, sleep blood pressure was significantly higher in the former group. ificantly fewer subjects given α-blockers had a controlled sleep blood pressure. Among α-blocker nonusers sleep blood pressure was the best controlled category, whereas in α-blocker users manual blood pressure had the highest rate of control. Generally, accounting for covariates of Finally, a limited negative dose-response relationship between α-blockade and dipping magnitude was also noticed. Conclusions: We found a significant negative association between adrenergic alpha-blockade and the magnitude of sleep-related blood pressure decline. Awaiting results from interventional studies, this may suggest a need to perform ambulatory monitoring in patients given alpha-blocking agents (or at least supine and standing measurements) and may partially clarify the inferiority of doxazosin in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT).