The effects of 3-n-butylphthalide(NBP) on the levels of 6-keto-PGF1 alpha, TXB2 and 6-keto-PGF1 alpha/TXB2 ratio were studied with methods of RIA. d-NBP and l-NBP(0.1-100 mumol.L-1) concentration-dependently increased 6-keto-PGF1 alpha release, decreased TXB2 release from neuronal cells, and significantly enhanced extracellular 6-keto-PGF1 alpha/TXB2 ratio in primary cultured rat cortical neurons exposed to hypoxic-hypoglycemic media for 5 h or hypoxic-hypoglycemic media for 5 h following normal media for 3 h. Aspirin(0.1-100 mumol.L-1) was also shown to inhibit TXB2 release from cortical neurons in a dose-dependent manner. However aspirin only increased 6-keto-PGF1 alpha/TXB2 ratio at low dose because aspirin inhibited both 6-keto-PGF1 alpha and TXB2 release simultaneously at large dose(10-100 mumol.L-1). This suggests that the action of l-NBP, d-NBP and dl-NBP on the increase of 6-keto-PGF1 alpha/TXB2 ratio might be one of the mechanisms in which NBP enhanced focal cerebral blood flow and improved ischemic brain damage.