Three experiments were conducted to test whether an electrical stimulation of the hippocampus had any effect on memory consolidation. Cats were trained in shuttle-box avoidance in Experiment 1, figural discrimination in Experiment 2, and delayed reaction in Experiment 3. The results revealed that a limbic seizure produced Z min after a trial had no effect on the memory consolidation (in Experiment 1 and 2), No difference was found between subjects with seizure and those without seizure in the number of trials needed to master the problem in both cases when a treatment was administered 1 min after a trial. On the other hand, serious retardation was caused by a hippocampal localized seizure with a minimum duration when it was given immediately after taking away the cue stimulus in the delayed reaction (Experiment 3).