The dysarthrias form a group of diverse, chronic motor speech disorders. The disorders of Parkinson's disease, stroke, traumatic brain injury, amyotrophic lateral sclerosis, and cerebral palsy are reviewed because they represent important clinical diagnoses in which dysarthria is a frequent and debilitating symptom. The roles played by speech-language pathologists include participation in differential diagnosis, provision of speech treatment, staging of treatment, and timely education so that clients and families can make informed decisions about communication alternatives. Both scientific and clinical evidence is presented that suggests that individuals with dysarthria benefit from the services of speech-language pathologists. Group-treatment studies, single-subject studies, and case reports illustrate the effectiveness of various types ofspeech treatment. Research into the effectiveness of augmentative and alternative communication systems for individuals with cerebral palsy is also presented.