Aims of the study were: 1. to establish the prevalence of CD44 protein expression in human astrocytomas; 2. to compare the distribution of the extracellular matrix in these tumors; 3. to investigate the relation between CD 44, the extracellular matrix proteins and the histological grade of the tumor. CD44, Type IV Collagen (Col IV), Laminin (LN), Fibronectin (FN), and Tenascin (TN) expression were detected by immunohistochemistry in formalin fixed paraffin embedded tissue samples of 52 astrocytic tumors: 35 glioblastomas (GB), 7 Anaplastic astrocytomas (AA) and 10 astrocytomas (A). The localization of Col IV was observed in the basement membrane of the vessel walls in most of the astrocytomas (88.4%) with a similar pattern obtained with LN staining. 7 of 10 A (70%), 2 of 7 AA (28%) and 9 of 35 GB (25.7%) showed LN positivity. There was a negative correlation between LN expression and tumor grade (p=0.03). FN was either localized in the basement membrane or showed thick multi-layered immunoreactivity of the vessel walls. FN expression was seen in 6 A (60%), 4 AA (57%) and all of 35 GB (100%). The FN distribution was not uniform and its staining intensity showed decrease in GB. 3A (30%), 3 AA (42%), 27 GB (77.1%) showed TN expression in the vessel walls and in some tumor cells of 19 GBs. TN expression was positively correlated with the degree of vascular endothelial proliferation in GB (p<0.05). The expression of CD44s wasseen as plasma membrane positivity of glioma cells in 5 of 10A (50%), 3 of 7AA (42.3%) and 29 of 35 GB (82.8%). The intensity of immunoreaction was quite strong especially near the vessels. There was a good correlation between TN and CD44s expression in human astrocytic tumors (p=0.005). No relationship was observed between GFAP, ECM proteins and CD44s expression. Both CD44s and TN expression showed increase with malignancy in astrocytomas. These findings indicated that the histological malignancy of the astrocytomas was correlated with expression of TN and CD44s. It was suggested that in astrocytomas there was a biological relationship only between CD44 and TN, but none with the other ECM proteins. TN may play a role in angiogenesis in human astrocytic tumors.