Vinpocetine, vincamine, aniracetam, and Hydergine, compounds with purported cognition activating activity, were evaluated for their ability to prevent scopolamine-induced and hypoxia-induced impairment of passive avoidance retention (24 hr) in rats. Vinpocetine (peak effect dose [PED]= 200 mg/kg PO), aniracetam (PED = 100 mg/kg PO), vincamine (PED = 30 mg/kg PO), and Hydergine (PED = 1 mg/kg PO) prevented memory disruption by scopolamine. Vinpocetine (PED = 3 mg/kg PO) and aniracetam (PED = 30 mg/kg PO) were also effective in preventing disruption of passive avoidance retention impaired by 7% oxygen hypoxia. In contrast, Hydergine (0.05 to 3 mg/kg PO) and vincamine (0.3 to 100 mg/kg PO) were not effective against hypoxia-induced impairment. Hydergine at doses greater than 10 mg/kg PO markedly impaired motor function. In both tests the protection was dose-related for all test substances in an inverted U-shaped manner. Mecamylamine (1, 3, 10 mg/kg SC), (-)-nicotine (0.1 to 0.4 mg/kg SC), apovincaminic acid (1-400 mg/kg PO) and pemoline (1-100 mg/kg PO) did not protect against memory impairment induced by either procedure. These data support the view that vinpocetine, a compound chemically distinct from the pyrrolidinones, has a cognitive activating ability as defined in models of both scopolamine-induced and hypoxia-induced memory impairment in rats.