Since the classic study by Perloff et al20 in 1983, the finding that ambulatory BPs are better cardiovascular risk predictors than are office BPs has been consistently demonstrated in hypertensive patients (treated,12 untreated,11,13 or both14), in diabetic patients,21 and in population-based cohorts,8- 10 but the superiority of ambulatory BP over office BP is not generally accepted.15 In RH patients, there is only 1 previous prospective study,16 published a decade ago. This pioneering study, possibly due to the few patients enrolled (n = 86) and, consequently, the reduced number of events (n = 21) observed during mean follow-up of 49 months, did not completely explore the relationships between ambulatory BP levels and cardiovascular outcome. Nevertheless, it demonstrated that RH patients in the highest tertile group of daytime DBP (>97 mm Hg) were at increased risk for future cardiovascular events and of progressing target organ damage in relation to those in the lowest tertile group after adjusting for age, sex, smoking, previous cardiovascular diseases, left ventricular hypertrophy on electrocardiography, and office BP. This study confirms this finding and further advances it by showing the relative prognostic values of daytime vs nighttime BPs and of SBP vs DBP vs PP. Regarding the prognostic importance of the ABPM diagnosis of true or white-coat RH, there is also only 1 previous study that addressed this issue.22 This study evaluated 276 patients with RH (although not all of them were using a diuretic), 130 with true RH, and reported that after mean follow-up of 5 years, true RH patients had a 2.4-fold (95% CI, 1.0- to 5.8-fold) increased risk of having a fatal or nonfatal cardiovascular event compared with white-coat RH patients after adjusting for age, smoking, low-density lipoprotein cholesterol level, diabetes mellitus, left ventricular hypertrophy on echocardiography, and office SBP. The present study corroborates this observation, with a very similar relative risk (2.1; 95% CI, 1.3-3.3), and advances it by demonstrating that true RH status is also an independent predictor of all-cause mortality and that its predictive value is additive to 24-hour ambulatory BP. The complete lack of any prognostic value of office BPs has been demonstrated in these 2 previous studies16,22 and confirmed in the present study. This finding reinforces the recommendation that antihypertensive drug treatment in RH patients should be driven by ABPM results and not by office BP measurements.