In a long-standing case of myxoedema with ataxia and dysarthria, neurophysiological investigations were carried out to assess how much of the ataxic dysbasic syndrome depended on the slowness of mechanical contraction and how much resulted from primary cerebellar involvement. It was observed that the Achilles reflexogram showed a marked prolongation of contraction and relaxation time and that in both quadriceps and triceps surae mechanical percussion induced a marked myxoedema and prolonged relaxation time. The EMG of these muscles during voluntary contraction and stopping reaction detected an excessive recruitment of the antagonistic muscles, starting without any abnormal delay, a finding at variance with a typical cerebellar pattern. Post-urographic analysis gave a pattern of oscillations still within the normal range. These findings suggest that the gait alterations of our patient depended on the increase in muscle contraction time and the consequent excessive recruitment of the antagonists.