Types of bilingualism qualitatively and quantitatively affect the dual competence and performance of bilinguals. In accordance with some research on mental representation, cognitive processes and bilingual memory, we can define as differential, differed and dynamic the type of bilingualism best suited to literary translation. Because it is differential (with separate contexts for each language) and differed (with the preceding acquisition of one language), this type of bilingualism is not interference-conducive. Also being dynamic (second language acquired through direct contact with referent), it enables translators to identify precisely and quickly some key components of the source-text sociolinguistic perceptions (registers, stylistic innovation, neologisms) and sociolinguistic patterns (societal and dialectal). An analysis of selected literary excerpts and translations shows this type of bilingualism at work: an efficient instrument, it serves two important goals in translation: preciseness and speed.