Abstract: Objective To investigate the difference in the vulnerability of carotid atherosclerotic plaques in patients with unilateral and bilateral intraplaque hemorrhage (IPH). Methods A retrospective analysis was conducted among 44 patients with unilateral IPH (30 cases) or bilateral IPH (14 cases) in the carotid plaques detected by magnetic resonance imaging (MRI) in our hospital between December, 2009 and December, 2012. The age, maximum wall thickness and incidence of fibrous cap rupture were compared between the two groups. Results Compared with those with unilateral IPH, the patients with bilateral IPHs had a significantly younger age (66.6 ± 9.4 years vs 73.7 ± 9.0 years, P=0.027), a significantly greater maximum plaque thickness (6.3±1.9 mm vs 5.0±1.3 mm, P=0.035) and a higher incidence of ulcers (50% vs 13.3%, P=0.025). Logistic regression analysis revealed a significant association between bilateral IPHs and the occurrence of ulcer with an odd ratio (OR) of 6.5 (95% confidence interval [CI]: 1.5-28.7, P=0.014). After adjustment for gender in Model 1, bilateral IPHs were still significantly associated with presence of ulcer (OR=5.7, 95%CI: 1.1-29.2, P=0.036). But after adjustment for age (P=0.131) or maximum plaque thickness (P=0.139) in model 2, no significant correlation was found between bilateral IPHs and the presence of ulcer. Conclusion Compared with patients with unilateral IPH, those with bilateral IPHs are at a younger age and have a greater plaque burden and a higher incidence of fibrous cap rupture, suggesting a greater vulnerability of the carotid plaques in patients with bilateral IPHs.