Cumulating evidence suggests that the establishment of high-quality phonological representations is the "cognitive precursor" that facilitates the acquisition of language (spoken, signed, and written). The authors present two studies that contrast the nature of bilingual profoundly deaf children's phonological representations derived from a spoken language and from a signed language using the framework of "functional equivalence" as outlined in McQuarrie and Parilla (2009). The authors argue further that a signed-language phonological system is suited in establishing the "functional" representational base that will support reading acquisition for bilingual deaf learners. They highlight rapidly developing empirical research on dual-language interactions between signed language and written language is highlighted, and discuss the need to take such data into account in any discussion of fundamental skills necessary to support reading achievement in bilingual profoundly deaf learners.