This is a study of two developmental speech production disorders, which emerge during the critical period of speech development between 2.5 and 12 years of age. During this critical period there is considerably greater brain plasticity for speech functioning which disappears following puberty. Our purpose is to determine how normal brain organization for speech production and perception develops during the critical period and how this normal pattern is altered when stuttering and phonological disorders become chronic problems, persisting throughout the life span. Functional MRI and magnetoencephalography (MEG) are non-invasive methodologies suitable for research in these disorders in children. New methodologies using fMRI and MEG provide the first opportunity for the study of speech production both in normally developing children as well as children and adults with stuttering and/or phonological disorders. Our hypothesis is that, with development, the brain organization for speech production becomes less distributed involving fewer brain regions, and that phonological processing mechanisms become lateralized to the left hemisphere during the critical period of speech development. This research will address whether the brain regions involved in speech are more diffuse and less selective in persons who develop chronic stuttering and phonological disorders, leading to a less efficient dynamic system for speech production.