It has been proposed that one can recognize a previously studied item based on the recollection of specific details of the study episode or based on a non-specific and context free sense of familiarity. Human lesion studies, single unit recordings in animals and brain imaging studies add to the converging evidence that both aspects of recognition memory are mediated by two medial temporal lobe systems: The perirhinal cortex and the hippocampus. In this talk it will be shown that familiarity-based and recollection-based recognition can be mapped onto spatially and temporally distinct parts of the ERP old/new effect. Familiarity-based recognition judgments are associated with a mid frontal old/new effect that onsets earlier and demonstrates a different scalp distribution than a parietal old/new effect that is associated with recollection-based recognition. It will be shown that this ERP dissociation holds for a variety of operational definitions of familiarity and recollection. However, a critical case for the generation of a familiarity signal appears to be the assessment of the global similarity between the first and second occurrence of an item. Whereas recollection presupposes the retrieval of associational, inter-item information. Results from recent ERP studies suggest that recognition memory for biologically relevant (emotional) events is characterised by different contributions of familiarity-based and recollection-based judgments as compared to recognition memory for neutral events. Implications of these findings for models of episodic memory as well as for the functional architecture of the medial temporal lobes will be outlined.