We describe a case of acute multifocal motor neuropathy with normal sensory conduction studies in the nerve segments of severe motor conduction block. Antiganglioside antibodies were not detected in serum and the patient recovered spontaneously. The clinical picture and course of time of the illness allowed the diagnosis of a Guillain-Barré syndrome (GBS). The electrophysiological findings closely matched the typical findings of chronic multifocal motor neuropathy with persistent conduction block. From these similarities, we conclude that acute and chronic forms of acquired demyelinating motor neuropathies have to be accepted as variants of acute GBS and chronic inflammatory demyelinating polyneuropathy (CIDP), respectively. We suggest that the conduction block cannot always be attributed to antiganglioside antibodies, as chronic cases without antiganglioside antibodies have also been reported and further elevation of antibody titres has been seen after spontaneous recovery.