These experiments examined the involvement of the intrinsic GABAergic system of the amygdaloid complex in the modulation of memory storage. Rats were chronically implanted with bilateral cannulae in the amygdala, trained in an inhibitory avoidance task, and given post-training bilateral intra-amygdala injections of either the GABA receptor antagonist bicuculline methiodide (BMI) (0.1-1.0 nmol) or the GABAA receptor agonist muscimol (0.001-0.1 nmol). As indicated by performance on a 48 h retention test, BMI enhanced retention of the inhibitory avoidance conditioning, while muscimol impaired retention. The memory-enhancement obtained with BMI (0.1 nmol) was produced by a dose lower than that necessary to induce convulsions. Post-training injections of BMI did not affect retention when injected into the caudate-putamen dorsal to the amygdala. These results suggest that the amygdaloid GABAergic system is involved in the modulation of memory storage.