The leaves of (Ginkgo)___- (biloba)___- L. and aqueous extract from them shortened the sleeping time induced in mice by anesthetics (hexobarbital, α-chloralose and urethane, i.p.). Two characteristic terpenoids in (G.)___- (biloba)___-, bilobalide and ginkgolide A, significantly shortened the sleeping time induced by anesthetics.A toxic substance, 4-O-methylpyridoxine (MPN), responsible for "gin-nan food poisoning" isolated from the seed of (G.)___- (biloba)___-, was not detected from the extract of the leaves of (G.)___- (biloba)___-. Therefore, the Ginkgo biloba extract has no toxicities for MPN.