Recent epidemiological studies have reported an association between carotid intima media thickness (IMT), ambulatory blood pressure (ABP) and absolute cardiovascular risk. To study the relation between white coat effect and vascular changes in hypertensives (HT), 57 essential HT (office blood pressure (OBP) 152.2 +/- 19.5/93.7 +/- 12.4 mmHg) were recruited (46.4 +/- 11.8 years old, 49 men). After antihypertensive drugs withdrawal, an ABP was performed (Spacelabs 90207). The right common carotid artery IMT 3 cm proximal to the bifurcation was examined by ultrasonography. IMT (0.59 +/- 0.09 mm; Software lotec system) were measured by a reader blinded to the ABP data. White coat hypertension (WCH) was defined by a mean day-time ambulatory BP (d-ABP) lower than the 90th percentile of the distribution of daytime ABP of a normotensive population reported by Verdecchia et al. (131/86 mmHg in women and 136/87 mmHg in men). [table: see text] White coat hypertension was found in 8 from 57 (14%) subjects. IMT was significantly increased in ambulatory HT when compared with white coat HT while age, sex ratio, OBP, smoking status were not different. In stepwise regression age and systolic d-ABP were the only determinants of IMT (p < 0.05). In our hypertensive population. ABP appears more closely related to IMT than OBP and IMT in sustained is greater than in white coat hypertensive.