The authors performed a multimodal electrophysiologic evaluation in nine patients belonging to four SCA17 (spinocerebellar ataxia type 17) families. Peripheral nerve and visual system were not involved. Brainstem auditory evoked potentials were constantly abnormal with central type lesions. Magnetic motor evoked potentials were abnormal only in the lower limbs, suggesting a length-dependent involvement of the pyramidal tract. Somatosensory evoked potentials were abnormal in almost all our patients, and abnormalities were consistent with a somatosensory pathway involvement along the brainstem.