Background Cardiovascular complications of Kawasaki disease (KD) are a common cause of heart disease in pediatric populations. Previous studies have suggested a role for endothelial progenitor cells (EPCs) in coronary artery lesions associated with KD. However, long-term observations of EPCs during the natural progression of this disorder are lacking. Using an experimental model of KD, we aimed to determine whether the coronary artery lesions are associated with down-regulation of EPCs. Methods To induce KD, C57BL/6 mice were administered an intraperitoneal injection of Lactobacillus casei cell wall extract (LCWE; phosphate buffered saline used as control vehicle). Study groups included: group A (14 days following LCWE injection), group B (56 days following LCWE injection) and group C (controls). Numbers of circulating EPCs (positively staining for both CD34 and Flk-1 while staining negative for CD45) were evaluated using flow cytometry. Bone marrow mononuclear cells were cultured in vitro to expand EPCs for functional analysis. In vitro EPC proliferation, adhesion and migration were assessed. Results The model was shown to exhibit similar coronary artery lesions to KD patients with coronary aneurysms. Numbers of circulating EPCs decreased significantly in the KD models (groups A and B) compared to controls ((0.017 +/- 0.008)% vs. (0.028 +/- 0.007)%, P<0.05 and (0.016 +/- 0.007)% vs. (0.028 +/- 0.007)%, P <0.05). Proliferative, adhesive and migratory properties of EPCs were markedly impaired in groups A and B. Conclusion Coronary artery lesions in KD occur as a consequence of impaired vascular injury repair, resulting from excess consumption of EPCs together with a functional impairment of bone marrow EPCs and their precursors. Chin Med J 2012;125(3):496-501