Thyrotropin-releasing hormone (TRH) has been reported to improve the clinical picture of patients with the predominantly cerebellar form of spinocerebellar degeneration. The authors performed a double-blind, double cross-over, four-month trial, where TRH, at the daily dose of 2 and 4 mg, and placebo were given intramuscularly over a period of one month each. Sixteen patients with Friedreich's disease and 14 patients with different forms of spinocerebellar degeneration completed the trial. Features of cerebellar involvement, such as dysarthria, dysmetria and stance ataxia, showed a slight but significant improvement during TRH treatment. TRH was well tolerated. Transient nausea was the most frequent side-effect.