Formalin-fixed paraffin-embedded tumor specimens from 90 patients with supratentorial astrocytic brain tumors were immunostained following microwave pretreatment using monoclonal antibodies against estrogen receptor (ER), progesterone receptor (PgR), and PS2 protein (PS2) and the streptavidin/peroxidase method. The immunohistochemical analysis was scored in a semiquantitative fashion incorporating both the intensity and distribution of specific staining (SCORE) and the immunohistochemical results were correlated with histologic grade of tumors and patient's sex and age. Strong PgR nuclear immunopositivity was observed in 27 of 46 (59%) glioblastomas, in 9 of 20 (45%) anaplastic astrocytomas, and in 2 of 24 (8%) astrocytomas. The mean PgR score was 18.5 in glioblastomas, 11.3 in anaplastic astrocytomas, and 0.9 in astrocytomas. The expression of PgR immunoreactivity appeared to be dependent on the age and independent of the sex of patients. All tumors were negative for ER and PS2 protein. Normal astrocytes remained consistently negative for both sex steroid receptors and PS2. Our findings indicate a consistent expression of PgR in a number of poorly differentiated tumors including glioblastomas and anaplastic astrocytomas contrasting with the low PgR score values found in benign astrocytomas. The absence of ER and PS2 immunoreactivities supports the hypothesis that estrogen receptor in astrocytic tumors is probably truncated. However, regional tumor heterogeneity may be a limiting factor for the use of ER, PgR, PS2 immunohistochemistry in the evaluation of routine pathology specimens examination.