The thalamus in a patient with Menkes kinky-hair disease showed lesions involving the large association and specific sensory relay nuclei and sparing the nonspecific sensory relay nuclei. The results confirm the findings of Iwata et al. [1979] but add the notion of a relative sparing of the microneurons which represent 40-50% of the normal neuronal population in the medialis formation and 35-40% in the posterior formation [Dom 1976]. Although axonal and/or cortical neuronal damage has contributed some retrograde lesions, a primary thalamic degeneration probably represents the most important pathogenetic factor. Whether this degeneration results specifically from the deficiency of enzymes operative in copper metabolism in some thalamic nuclei only remains purely speculative. Its clinical significance within the syndrome dominated by a severe psychomotor retardation cannot be evaluated.