We studied the relationship between circadian blood pressure changes and development of early carotid atherosclerosis in 208 hypertensive and 216 normotensive patients older than age 55 years. Blood pressure patterns were evaluated noninvasively with a long-term blood pressure monitor, and extent of atherosclerosis was measured as the intima to media wall thickness (IMT) of the common carotid artery. No significant differences regarding age, sex, smoking, diabetes, cholesterol, and triglycerides were found between both patient groups. The age-adjusted IMT was significantly larger in the hypertensive patients (1.34 mm [95% confidence interval 1.24, 1.44] versus 1.18 mm [1.14, 1.22]; p < 0.05). However, after adjustment for diurnal systolic blood pressure variability, which was significantly increased in the hypertensive group, the significant IMT difference between both patient groups was no longer observed (1.32 mm [1.27, 1.37] versus 1.29 mm [1.25, 1.33]). Multivariate regression analysis revealed the diurnal systolic blood pressure variability as the strongest predictor for IMT. The IMT was most increased in hypertensive patients with increased diurnal systolic blood pressure variability and additional nocturnal blood pressure increase (1.64 mm [1.45, 1.83]. The odds ratio of having early atherosclerosis (age-adjusted IMT > 1.5 mm) increased with raised diurnal systolic blood pressure variability (> 15 mm Hg) in both groups (normotensive: 8.5 [2.30]; hypertensive: 12.6 [4, 43]). The diurnal systolic blood pressure variability is the strongest predictor of early carotid atherosclerosis measured with B-mode ultrasonography and is useful to define the risk-benefit ratio of therapeutic approaches, particularly in patients with only slightly elevated blood pressure levels.