In the current study, the authors sought to assess whether the time rate of systolic and diastolic blood pressure variation is associated with advanced subclinical stages of carotid atherosclerosis and plaque echogenicity assessed by gray scale median. The authors recruited 237 consecutive patients with normotension and hypertension who underwent 24-hour ambulatory blood pressure monitoring and carotid artery ultrasonography. There was an independent association between low 24-hour systolic time rate and increased echogenicity of carotid plaques (adjusted odds ratio for highest vs lower tertiles of gray scale median, 0.470; 95% confidence interval, 0.245-0.902 [P = .023]). Moreover, increased nighttime diastolic time rate independently correlated with the presence (adjusted odds ratio, 1.328; P = .015) and number of carotid plaques (adjusted odds ratio, 1.410; P = .003). These results indicate differential associations of the systolic and diastolic components of time rate of blood pressure variation with the presence, extent, and composition of carotid plaques and suggest that when blood pressure variation is assessed, both components should be considered.