This population-based study refers to 78 Swedish children with non-progressive ataxia from a total population of 3.1 million inhabitants. Inclusion criteria were ataxic gait without any signs of spasticity, dyssynergia, dysmetria and intention tremor. CT and/or MRI studies were available from 70 patients (90%). Infratentorial pathology was revealed in 27%, and findings were considered normal in 61%. If CT was normal, of recent date and of good quality, MRI did not add any new information. In half of the cases with pathological CT, however, MRI provided new information. The origin was considered prenatal in 45% (familial in 17%), perinatal in 4% and unclassifiable in 51%. 60% were mentally retarded; in the rest, cognitive development was near normal (18%) or normal (22%). Speech development was delayed in 88%, and 58% had visual dysfunction.