The present experiments examined the effects of posttraining intra-dorsal striatal (i.e., caudate-putamen) injections of the phospholipid methylcarbamyl platelet-activating factor (mc-PAF) and the platelet-activating factor (PAF) antagonist BN 52021 on memory using a striatal-dependent cued water maze task. Male Long-Evans rats received an eight-trial training session in which a visibly cued escape platform was located in a different quadrant of the maze on each trial, followed by an intrastriatal injection of mc-PAF (0.5, 1.0, or 2.0 micrograms/0.5 microliter), BN 52021 (0.25, 0.5, or 1.0 microgram/0.5 microliter), or vehicle (DMSO; 0.5 microliter). On a retention test 24 h later, the escape latencies of rats given mc-PAF (1.0, 2.0 micrograms) wee significantly lower than those of vehicle-injected controls, indicating a memory enhancing effect of mc-PAF. The retention test escape latencies of rats given BN 52021 (0.5, 1.0 microgram) were significantly higher than those of vehicle-injected controls, indicating a memory impairing effect of BN 52021. Injections of mc-PAF or BN 52021 did not affect retention when administered 2-h posttraining, indicating a time-dependent effect of the drugs on memory storage. The findings indicate a role for endogenous PAF function in striatal-dependent memory processes.