The study of phonological development has important implications for the diagnosis, understanding, and treatment of developmental language disorders. It also has implications for the understanding of language patterns in stuttering, disfluency, aphasia, bilingualism, second language learning, and dementia. Recent computational advances now make it possible for researchers to link high quality digital recordings to phonological and phonetic transcriptions. Using standards such as Unicode, IPA, and XML, and the infrastructure developed in the CHILDES Project, the PhonBank database project now provides universal Internet access to large corpora of transcripts linked to audio for the study of phonological developemnt. PhonBank also provides the Phon program that automates creation and analysis of these new corpora. The construction of this database is being be supported by a group of 60 researchers and their students who have agreed to contribute already collected and transcribed corpora from children learning 25 different languages. Subjects include bilingual children, normally-developing monolinguals, and children with language disorders. The data are being structured to facilitate testing of models regarding babbling universals, variant paths in segmental and prosodic development, markedness effects, prosodic context effects, segmentation patterns, statistical learning, frequency effects, interlanguage transfer, diagnosis of disability, stuttering patterns, disfluency patterns, and the effects of morphology and syntax.