BACKGROUND To determine whether automated office blood pressure (AOBP) readings are associated with left ventricular mass (LVM) index as closely as those of 24-h ambulatory blood pressure (ABP) and also to confirm that the values of the two methods are comparable in the appraisal of blood pressure in a European population referred for suspected hypertension. METHODS In a sample of 90 individuals with office hypertension, we compared AOBP to awake systolic ABP measurements (ABPM) values and their associations with LVM indices, expressed as LVM divided by body surface area (LVMIBSA) and by height(2.7) (LVMIH). RESULTS Mean awake systolic ABP was 136 +/- 16 mm Hg and mean systolic AOBP was 140 +/- 15 mm Hg (P < 0.002). Mean awake diastolic ABP was 87 +/- 11 mm Hg and mean diastolic AOBP was 88 +/- 12 mm Hg (P = 0.08). AOBP readings were as closely associated with LVMIBSA (r = 0.37) as were those of awake systolic blood pressure (SBP) (r = 0.37). The correlation between LVMIH and both mean awake systolic ABP and mean systolic AOBP was r = 0.37 (P < 0.001) and r = 0.34 (P = 0.001), respectively. CONCLUSIONS High-quality AOBP readings and ABP measurements correlate equally well with LVM indices, further supporting the use of AOBP in the clinical setting. Moreover, readings from both techniques are comparable in the assessment of blood pressure.