The effects of oxiracetam and piracetam were compared in learning and memory tests in rats and mice. In the dose range examined, the two nootropics were equally active in reducing the amnesia induced by cerebral electroshock in the mouse. Step-down retention performance, however, was distinctly improved by oxiracetam but unaffected by piracetam, no matter whether it was given before or immediately after the learning trial. Oxiracetam also improved acquisition performance in aged (24- to 27-month-old) rats in an active-avoidance situation at doses of 30 and 100 mg/kg i.p. whereas piracetam showed no effect at 100 mg/kg i.p.