The first weeks of aphasia are called the acute stage. The rapid change and possible fluctuation of language deficits at that stage as well as concurrent phenomena such as drive disturbances, apraxia, or perseveration pose particular requirements for aphasia diagnosis. Professional language diagnosis in a stroke unit is necessary for detailed description of the language deficits, differential diagnosis of concomitant cognitive or functional disturbances, and a description of the dynamics of the deficits to start with specific therapeutical interventions as soon as the patient's health status allows. There are three published German aphasia test batteries especially constructed for diagnosis of acute aphasia language deficits. They differ with respect to content and pragmatic aspects and offer a range of applications, including the diagnosis of aphasia, recommendations for therapy, and the use in scientific studies.