A primary goal of this study is to ascertain regions of the human genome which show genetic linkage to stuttering. Genetic linkage will be determined by first obtaining genomic DNA from both affected and unaffected adults and children from families containing pairs of individuals who stutter as adults. Individuals who stutter from genetically isolated populations will also be sampled. Phenotype will be assigned by a speech-language pathologist, and DNA samples will be obtained from affected and unaffected family members from 2 cc. of saliva or from 20 cc. of blood. These DNA samples will then be genotyped using markers distributed across the human genome. The genotypic information analyzed to determine which markers or variants show linkage to stuttering. The initial goal of this study is to identify specific genetic variants, which predispose individuals to stuttering. No genetic information will be provided back to participants. A secondary goal of the study will be to perform broad clinical evaluations of the individuals found to have mutations that cause stuttering. These will take place at the NIH Clinical Center and will include standard procedures including history and physical, neurological exam, audiological exam, ophthalmologic exam, electromyographic (EMG) exam, electroencephalography (EEG), X-rays, speech evaluation, and brain imaging including MRI and fMRI.