The purpose of this study was to explore the feasibility of ¹¹C-choline in the assessment of the degree of inflammation in atherosclerotic plaques. Uptake of ¹¹C-choline was studied ex vivo in tissue samples and aortic sections excised from 6 atherosclerotic mice deficient for both low-density lipoprotein receptor and apolipoprotein B48 (LDLR^−/−ApoB^100/100) and 5 control mice. The autoradiographs were compared with the immunohistology of the arterial sites. The uptake of ¹¹C-choline (percentage of the injected activity per gram of tissue) in the atherosclerotic aortas of the LDLR^−/−ApoB^100/100 mice was significantly higher (1.9-fold, P = 0.0016) than that in the aortas of the control mice. The autoradiography analysis showed significantly higher uptake of ¹¹C-choline in the plaques than in healthy vessel wall (mean ratio, 2.3 ± 0.6; P = 0.014), prominently in inflamed plaques, compared with noninflamed plaque areas. We observed a high ¹¹C-choline uptake in the aortic plaques of atherosclerotic mice. Our data suggest that macrophages may be responsible for the uptake of ¹¹C-choline in the plaques.