This chapter explores various aspects and assumptions of models of bilingual language processing and organization. A brief overview of theoretical language models is provided to include a discussion of the distinction between compound and coordinate bilingualism, as well as models of connectionism, hierarchical structures, and a recently proposed model of language acquisition. The underlying assumptions of these theories and models are assessed with a focus on inter-language processing and organization. There are many experimental designs that allow for the analysis of behavioural data. Various experimental results obtained using tasks that provide insight into the processing of language through behavioural responses are discussed in relation to learning and memory. The chapter explores findings related to how languages are processed in terms of their lexical units and the underlying nature of these representations. Although the structure of language can impact its processing across languages, the inherent properties of the representations play a key role, as well.