A patient had a paraneoplastic autonomic, then sensory, then sensory-motor neuropathy with small cell lung carcinoma and a high titer Anti-Hu antibody to nuclei of neuronal cells. As an unusual finding there was electrophysiological and pathological evidence of demyelination and a peripheral nerve microvasculitis. The relationship of microvasculitis and peripheral nerve demyelination is discussed and their occurrence with paraneoplastic anti-Hu-associated sensory neuropathy is suggested not to be by chance.