Immunohistochemical study of gliomas was maed using the indirect Avidin-Biotin Complex(ABC) method in order to investigate the presence and patterns of distribution of GFAP, neurofilament, and S-100 protein in 37 cases of human gliomas. Generally, two immunostaining patterns were observed; perikaryal and diffuse fibrillary background staining. All of the glial tumor cases were stained positively for GFAP except for the 3 oligodendrogliomas. The S-100 protein was sensitive for all the glial tumors and for neurofilament, in about half of the cases. These observations support previous reports that GFAP is specific for astrocytes, and that S-100 protein is sensitive, but not specific for glial tumors. Furthermore, our data suggest that immunostaining patterns of G.M. is different from that of astrocytoma grad II and III.