The nature of the bilingual mental lexicon and how the L1 and the L2 interact in language production and processing has been the focus of decades of research from linguistic, psycholinguistic and neurolinguistic perspectives. In spite of this significant body of evidence, the degree to which the L1 influences L2 production and processing remains an area of debate, especially with respect to formal features such as grammatical gender. While it is clear that non-nativelike production and processing of L2 grammatical gender persist even in highly-proficient adult bilinguals, the underlying representation of the L1 and L2 gender features and how this representation affects the use of gender in the L2 is currently unclear. Furthermore, there is no evidence at present regarding the nature of the L1-L2 grammatical gender system when the L1 and the L2 have asymmetric gender systems (in other words, differ in number of gender values), as is the case with German, which bears three gender values (masculine, feminine and neuter), and Spanish and French, which each display two gender values (masculine and feminine). This dissertation investigates the representation of and interactions between the L1 and the L2 at the level of the formal gender feature, with a particular focus on language pairings with asymmetric gender systems. Through complementary data from L2 production and processing, I examine the representation of the asymmetric grammatical gender systems in the mental lexicon of L1 Spanish-L2 German and L1 French-L2 German bilinguals and the consequences this asymmetry between the L1 and L2 gender systems has on gender use strategies in the L2. From the perspective of bilingual lexical access, this research contributes new evidence to inform existing psycholinguistic theories of L1-L2 gender interactions and also proposes the Asymmetric gender representation hypothesis, a new model to account for the unique integrated nature of the gender system in bilinguals with L1-L2 asymmetric gender systems. From a language acquisition perspective, the present study provides new data on L2 gender use strategies with asymmetric gender systems, formulating the L1 transfer continuum, which extends existing proposals to include the degree of (a)symmetry between the L1 and the L2. This research also connects theoretical proposals regarding gender agreement in functional-lexical code-switches (specifically, switches within the Determiner Phrase such as dieGER-F mesaSPA-F or elSPA-M TischGER-M) to bilinguals’ preferences in code-switching between two languages that display formal gender. Taken together, all of these complementary perspectives addressed in this dissertation offer a well-rounded perspective of grammatical gender in asymmetric gender systems specifically, and contribute novel evidence regarding the interactions between the L1 and the L2 in the bilingual mental lexicon in general.