Bilingualism has become common. Infants' auditory cortex undergoes structural maturation during the first three years (Yakovlev & Lecours, 1967). They develop an auditory capacity to specifically recognize acoustic patterns used in their native language (e.g., Kuhl et al. 1992). Bilinguals, compared to monolinguals, are exposed to and learn to identify greater number of speech sounds. We hypothesize that distinguishing between and storing larger inventories leads to the expansion of auditory cortical areas and the establishment of denser connections within subregions. We employ cutting-edge neuroimaging approaches to determine the correlation between the size of auditory cortex and the size of the speech sound pool in different language pairs. The phonetic disparities between language pairs are parametrized for comparison.