Abstract: Objective: We aimed to find out the presence of endothelial chimerism and its relationship with progress of chronic renal allograft nephropathy （CAN）. Methods: We studied samples from 29 dysfunctional nephrectomized renal transplants of female recipients who received the kidneys from male donors for the presence of endothelial cells of recipient origin. Formalin-fixed, paraffin-embedded tissue sections of renal samples were examined by fluorescence in situ hybridization for the presence of endothelial cells containing two X-chromosomes using biotinylated Y-chromosome probe and digoxigenin labeled X-chromosome probe. Endothelial staining was performed on the sequential section with anti-CD31 monoclonal antibody in immunohistochemistry technique. Results: The FISH methods did identify endothelial cells of recipient origin. The density of CD31 positive peritubular capillaries were decreased with the progressing of chronic allograft nephropathy. The density of PTC was 14.52±4.85/5285.5m², and the percentage of endothelial chimerism was 0.16±0.04. There was no correlation between the density of CD31 positive peritubular capillaries and the ratio of microvessels in which endothelial cells were replaced by recipients（r=0.13, P＞0.05）. Conclusion: The deterioration of chronic allograft nephropathy has no relation with endothelial cell chimerism.