Hereditary ataxia was diagnosed in three smooth-haired fox terrier puppies from Sweden, 25 years after the previous known case in the breed. In addition to the characteristic spinal cord pathology, brain involvement was evident clinically, in the form of behavioural changes and bilaterally decreased menace responses, and histopathologically, with degenerative changes in the brainstem. The striking similarities to hereditary ataxia in the Jack Russell terrier suggest the same disease process in both breeds. A common ancestor, a female dog born in 1951 and considered a carrier of the disease at that time, was found in both the maternal and paternal lines of the three puppies.