Systemic, post-training injections of d-amphetamine improve memory in a variety of learning situations. Evidence from self-stimulation and intra-striatal injection studies suggests that this effect may be a result of the amphetamine-promoted release of endogenous dopamine from nigro-striatal neurons. In the present study this hypothesis was supported by the demonstration that destruction of these neurons with intra-nigral injections of 6-hydroxydopamine eliminate the memory-improving effect of systemic, post-training injections of amphetamine.