It is clear, even to the casual observer, that stuttering is associated with aberrant speech breathing. Moments of stuttering may involve explosive release of air, complete cessation of airflow, and even speaking on inspiration. However, while many therapies and intervention programs require participants to alter their breathing patterns, it is not known whether aberrant breathing is a cause or a result of stuttering. A third possibility is that certain features of speech breathing, such as high lung volume, may trigger stuttering. This presentation will report preliminary findings of a large collaborative program of research that is investigating these hypotheses.