Drawing on data from three bilingual Lebanese Arabic-English children, this paper explores whether bilinguals develop one or two phonological system, proposing a refinement of the notion of a system, based on insights from recent phonetic and sociolinguistic work on speech variability. The findings demonstrate that bilinguals develop separate /l/ production patterns for each of their languages, similar to those of monolinguals, and that the crosslinguistic interaction, restricted to the bilingual mode, constitutes a sign of their sociolinguistic competence.