Objective: To investigate the changes and significance of microvessel density(MVD) in bone marrow of patients with aplastic anemia. Methods: 30 aplastic anemia cases,20 hyperplastic anemia cases,and 20 normal individuals′ paraffin-embedded bone marrow biopsys were stained with HE and CD34 by immunohistochemistry method respectively;and the vol% of hematopoietic tissue area in bone marrows were detected accordingly. Results:The difference between the MVD of HE and CD34 was not significant in aplastic anemia cases ,and the difference between the MVD of HE and CD34 was not significant in normal individuals either. While the MVD of HE was significantly lower than that of CD34 in hyperplastic anemia cases. The difference of the MVD between light and heavy pathogenetic condition in aplastic anemia cases was significant.The MVD of CD34 were significantly different among the cases of aplastic anemia, hyperplastic anemia,and normal individuals.The MVD showed significant linear correlation with the vol% of hematopoietic tissue area (r=0.74,P