Fifteen patients with Friedreich’s ataxia (FA) and 15 others with olivopontocerebellar atrophy (OPCA) were evaluated with a comprehensive neuropsychological battery of tests. They were pair-matched with normal controls for age, sex and education. Depressed patients were excluded from the study as were those with extrapyramidal signs. The following results were obtained: (1) the Raven test, untimed block design performance in OPCA and quantitative analysis of Rey figure drawing revealed a visuospatial deficit suggestive of a mild parietal-like syndrome; signs of mild frontal-like syndrome were also found; (2) cognition was slowed in the FA group; (3) simple visual and auditory reaction times were increased in both patient groups. It appears that the cerebellum may interfere indirectly with cognition through various physiological and neurochemical 2-way cerebellocortical loops. Finally, the cerebellum seems to interfere directly also with basic speed of information processin