In order to investigate the expression of androgen receptor in meningiomas and its relation to tumor proliferative potential, we examined the expression of AR and proliferating cell nuclear antigen by avidine biotin complex immunohistochemistry in 39 cases of meningiomas. Of the 39 cases of meningiomas, 20 showed positive AR immunoreactivity. The AR expression positivity rates were 31 % in benign meningiomas, 58 % in atypical meningiomas, 87.5 % in malignant meningiomas, respectively. In addition to the tumor cells, cells of microvascular endothelial proliferation were frequently AR positive. Malignant meningiomas had a significantly higher percentage of AR positive cells compared with atypical and benign meningiomas . The mean proliferating cell nuclear antigen labeling index was significantly higher in the malignant meningiomas when compared with atypical meningiomas and benign meningiomas . AR positive meningiomas had higher PCNA LI than AR negative meningiomas . The expression of AR in tumor tissues was significantly related with PCNA LI. These data indicated that AR in the meningiomas was correlated with histological grade and AR might participate in the growth of these tumors and tumor angiogenesis. The measurement of AR in these tumors may indirectly represent tumor growth potential. In order to investigate the expression of androgen receptor in meningiomas and its relation to tumor proliferative potential, we examined the expression of AR and proliferating cell nuclear antigen by avidine biotin complex immunohistochemistry in 39 cases of meningiomas. Of the 39 cases of meningiomas, 20 showed positive AR immunoreactivity. The AR expression positivity rates were 31% in benign meningiomas, 58% in atypical meningiomas, 87.5% in malignant meningiomas, respectively. In addition to the tumor cells, cells of microvascular endothelial proliferation were frequently AR positive. Malignant meningiomas had a significantly higher percentage of AR positive cells compared with atypical and benign meningiomas. The mean proliferating cell nuclear antigen labeling index was significantly higher in the malignant meningiomas when compared with atypical meningiomas and benign meningiomas. AR positive meningiomas had higher PCNA LI than AR negative meningiomas The expres sion of AR in tumor tissues was significantly related with PCNA LI. These data indicated that AR in the meningiomas was correlated with histological grade and AR might participate in the growth of these tumors and tumor angiogenesis. The measurement of AR in these tumors may indirectly represent tumor growth potential.