Three neuropsychological experiments on a group of 16 cerebellar patients and 16 age-and education-matched controls investigated the effects of damage to the cerebellum on English grammatical morphology across production, comprehension, and grammaticality judgment tasks. In Experiment 1, participants described a series of pictures previously used in studies of cortical aphasic patients. The cerebellar patients did not differ significantly from the controls in the total number of words produced or in the proportion of closed-class words. They did differ to a marginally significant extent in the production of required articles. In Experiment 2, participants identified the agent in a series of aurally presented sentences in which three agency cues (subject–verb agreement, word order, and noun animacy) were manipulated. The cerebellar patients were less affected than the controls were by the manipulation of subject–verb agreement to a marginally significant extent. In Experiment 3, participants performed a grammaticality judgment task on a series of aurally presented sentences. The cerebellar patients were significantly less able to discriminate grammatical and ungrammatical sentences than the controls were, particularly when the error was of subject– verb agreement as opposed to word order. The results suggest that damage to the cerebellum can result in subtle impairments in the use of grammatical morphology, and are discussed in light of hypothesized roles for the cerebellum in language.