Among 103 patients with degenerative cerebellar ataxia, incidence reached a peak in the age group 0 to 19 years and a greater peak in the age group 50 to 69. In the adult group, males predominated 2:1. Duration of the ataxia ranged from 1 month to 41 years, with a median of 3 years. Only 15 patients revealed a history of an identical or related condition in other members of the family. In most patients, the cause was either uncertain or undetermined. In most patients, ataxic gait preceded and was more pronounced than limb ataxia. The group was classified into normoreflexic, hyporeflexic, and hyperreflexic forms. Patients with normoreflexic cerebellar ataxia had a paucity of other neurologic signs. In the hyporeflexic form, signs referable to the spinal cord and peripheral nerves were prominent, as were pes cavus and scoliosis. The hyperreflexic form demonstrated a predominance of pyramidal and extrapyramidal signs. Cranial nerve, brain stem, and mental signs occurred in the 3 forms of ataxia with approximately equal frequency. In 2 exceptional syndromes, limb ataxia was more prominent than gait ataxia.