We previously reported (Europ, Neurol., 3, 347-364, 1970) on two clinical observations of progressive myoclonus epilepsy in the same family. Now, we complete the clinical study showing the neuropathological findings concerning one of the two patients who died at the age of twenty. Degenerative neuronal alterations were found involving the olivo-cerebello-rubral system and, in a minor degree, the brain stem and thalamic structures. No Lafora bodies were found. These pathological features make it possible to suggest a differentiation from a first group of progressive myoclonus epilepsy (Unverricht-Lundborg) and another group (with epileptic manifestations) of dyssynergia cerebellaris myoclonica (Ramsay Hunt). We agree with the suggestion of other authors that it is difficult to establish precise differentiations between these groups at neuropathological level. We think however that the distinction is still possible on the basis of the clinical picture. Our observations cupport the hypothesis that our patient is an "abiotrophic" case of Unverricth-Lundborg syndrome, as we previously had suggested on clinical and especially neurophysiological findings.