We describe a patient with chronic asymmetric motor neuropathy, which began in the upper extremity. The paretic muscles showed abundant fasciculations and myokymia but only little amyotrophy. Electrophysiologic examination revealed proximal multifocal persistent conduction block (CB) not located at the usual entrapment sites, and arrhythmic isolated or grouped fasciculation potentials originating distally on blocked axons. Over the years, new CBs developed, which led to tetraplegia, and amyotrophy slowly increased with progressive denervation. This patient differs from the cases of chronic acquired demyelinating polyneuropathy described in the literature by the absence of sensory deficit and the proximal location of CB.