This article aims to define recognition memory and a variety of models which intent to explain it, as well as to describe the scientific findings that support the existence of the two processes involved in this type of memory (recollection and familiarity), and the methods used through the last decades to measure and estimate these processes. So, the outcomes from processing speed show that familiarity is faster than recollection, which suggest that there are two different processes. Likewise, receiver operating characteristic studies point out that at least two components are necessary to the recognition memory, whereas event related to potentials studies show that both recollection and familiarity present distinct electrophysiological correlates. The last finding refers to amnesic patient studies which reveal a more severe recollection deficit than familiarity.