The present paper discusses IMPLICIT memory (compared to explicit memory) as a new phenomenon in memory research. First, ideas about IMPLICIT memory are considered very briefly from historical point of view. Then, as in recent studies, two lines of research are discussed; i.e., subliminal stimuli and repetition priming studies. These studies, especially priming studies, show that explicit memory are affected differently by various variables. While explicit memory tests are affected by the levels-of-processing and the interval between encoding and retrieval stages (forgetting effect), IMPLICIT memory tests are not affected. On the other hand, while IMPLICIT memory tests are sensitive to modality and mood changes, manipulated both at encoding and at retrieval, memory tests are unaffected. The findings related to amnesic patients are impaired with respect to explicit memory and are intact with respect to IMPLICIT memory.There are two theoretical explanations for this double dissociation between explicit and IMPLICIT memory. The processing view suggests that there is a single and integrated memory system and the discrepancy between explicit and IMPLICIT memory are explained the different natures of relation between encoding and retrieval processes or procedures. The multiple memory systems view, which is more promising and supported by empirical evidence, claims that each of these two types of memory is supported by an independent and separate system(s). Although these systems interact with each other, they follow different rules, however.