We report the case of a 29-year-old male patient with cerebellar ataxia of Holmes' type. The combination of progressive cerebellar ataxia and hypogonadotrophic hypogonadism is a rare distinctive syndrome which was first described by Holmes in 1907. Early diagnosis is desirable because replacement of testosterone may allow normal sexual development. MRI showed severe combined superior vermian and cerebellar hemisphere atrophy. Comprehensive neuropsychological testing pointed to a more widespread cerebellar mediated functional CNS involvement in the earlier stages of this ataxic syndrome than previously described in mentally not retarded subjects.