AbstractUsing computed electro‐nystagmography, quantitative assessment of the cerebello‐vestibular function was performed in 13 patients with congenital hypothyroidism, aged 3 to 20 yrs, during adequate long‐term replacement therapy. Thirty‐two age‐matched children and 127 patients with confirmed cerebellar, brain stem or vestibular disorders served as controls. Routine neurological tests for body equilibrium revealed an abnormal finding in only two patients (15.3%). In contrast, the combination of spontaneous and positional nystagmus, caloric test, visual pendular rotation test, eye‐tracking test and optokinetic nystagmus test revealed abnormalities in 76.9% (10/13). Five patients had impairment of peripheral vestibular pattern, whereas 5 showed vestibulo‐central pattern. The critical factors producing the two different patterns appear to be the initial serum thyroxine level and the time of initiation of the therapy. Severe and long‐standing deficiency of thyroid hormone was associated with vestibulo‐cerebellar impairment, while mild hypothyroidism was associated with vestibular abnormalities. These results confirmed a high incidence of cerebello‐vestibular dysfunction as a neurological sequela of congenital hypothyroidism, even with early replacement therapy. The method affords a tool for objective evaluation of ill‐defined ‘clumsiness’ in