This chapter deals with acquired neurogenic speech disorders (aphasia) following a stroke. The neurological processes of ischemic and hemorrhagic cerebral infarction are presented and the causes and treatment options are explained. After a basic description of the different forms of acquired brain damage, the effects of brain trauma, brain tumors, cerebral hemorrhage and circulatory disorders on the ability to language are mentioned. The different aphasia syndromes are explained using language examples. In addition to the neurolinguistic basics of aphasic language disorders, tests and procedures for diagnosis and therapy in clinical linguistics are also presented.