Stroke is the leading cause of serious disability among adults in the United States.1 Aphasia, a language disorder caused by damage to the speech and language regions in the left hemisphere, is one of the most devastating results of stroke and affects individuals' ability to communicate effectively. Broca's aphasia is one of the most common types of aphasia and is characterized by restricted speech output, often not exceeding 1- 3 words per utterance, and relatively preserved auditory comprehension. Once in the chronic phase, most patients with Broca's aphasia experience very limited improvement in speech production. In a recent study2, we showed that patients with Broca's aphasia could produce fluent speech while mimicking an audio/visual speech model. In short, patients were able to mimic a one-minute script that was prerecorded and presented so that the speaker's mouth was seen on a computer screen and the speech was heard via headphones. We refer to this effect as speech entrainment, where the audio/visual speech model yokes the speech of the non-fluent patient, allowing him/her to produce fluent speech. Whereas speech entrainment might be important for understanding normal speech production, we propose that it could have important implications for rehabilitating patients with Broca's aphasia by allowing them to practice fluent speech production, something that is inherently very difficult for this population. The purpose of this pilot project is to estimate effect sizes associated with improvements in speech production as a result of speech entrainment treatment (SET). If SET results in medium or large effect sizes for improvements in speech production, we will move on to a larger trial where the effects of SET can be established and compared to other kinds of treatments for speech production in aphasia. The second goal is to understand cognitive-linguistic factors in relation to patients' ability to speak with the aid of speech entrainment. This will allow us to identify factors that are contraindicative for SET (to define inclusion/exclusion criteria in a larer trial) as well as relate our findings to contemporary models of speech processing. The long-term goal is to develop a treatment approach that can be used to improve speech production in Broca's aphasia, something that has been shown to be particularly resistant to treatment. We emphasize that the treatment approach presented here represents a starting point in our development; more data will allow us to modify SET and better tailor it towards specific patients.