The effects of serum of patients with Kawasaki disease on the platelet derived growth factor-B (PDGF-B) chain protein expression in monocytes were studied by immunocytochemical method and the effects of the serum on the endothelial cellular (EC) apoptosis were observed by flow cytometric technique. It was found that the serum of patients with Kawasaki disease induced significantly the expression of PDGF-B chain protein. Likewise, EC apoptosis was increased significantly in the experimental group as compared with the control group (P < 0.01). The results suggest that PDGF in monocytes increase and EC apoptosis play an important role in the development of coronary artery complication in Kawasaki disease.