5-lipoxygenase (5-LO) is a key enzyme in the synthesis of leukotrienes (LTs), that might promote carcinogenesis. We investigated 5-LO expression and examined whether the 5-LO pathway is associated with the proliferation of human brain tumors.We immunohistochemically evaluated the profile of 5-LO expression in various types of brain tumors obtained from 42 patients, and examined the proliferative effects of the 5-LO pathway in human glioma cell lines using a proliferation assay.Immunohistochemistry of glioblastomas, astrocytomas, meningiomas, medulloblastomas, craniopharyngiomas, ependymomas, neurinomas, oligodendrogliomas, malignant lymphomas, dysembryoplastic neuroepithelial and metastatic brain tumors revealed 5-LO expression in the cytoplasm and nuclei or nuclear envelopes of tumor cells. The 5-LO inhibitor A861 and the LTA4 hydrolase inhibitor Bestatin dose-dependently suppressed the proliferation of A172 cells, a glioma cell line.We confirmed the expression of 5-LO in various human brain tumors and demonstrated the partial suppression of tumor growth by inhibitors of the 5-LO-LTA4 hydrolase pathway in human glioma cell lines. The 5-LO-LTA4 pathway might play roles in the proliferation of human glioma cells.