This chapter provides an overview of some of the most influential and models of how bilinguals represent their languages in memory. It also provides an overview of the different types of memories that have been identified in the bilingual cognitive literature, followed by an evaluation of the one- versus two-memory hypotheses. The chapter introduces the bilingual interactive activation plus model that assumes activation of multiple levels during bilingual word recognition. It proposes a bilingual memory representation based on how the bilingual’s languages are learned. Models that assume a memory structure composed of language-specific mental lexicons and a shared general memory store are evaluated. The shared memory store hypothesis was seen as accurately describing bilingual memory representation at the semantic or meaning level. Studies of semantic memory utilize reaction time as a measure of retrieval or search time. The more semantic senses shared between words across languages, the more identical the concepts are shared as well.