Guillain-Barré syndrome (GBS) is a heterogeneous disorder according to clinical, electrophysiological, immunologic and pathologic findings. It has usually been considered as an immune-mediated polyneuropathy clinically characterised by acute symmetric muscle weakness and areflexia. We describe a patient who, after a Campylobacter jejuni infection, developed an acute motor-sensory neuropathy with marked and persistent asymmetry of clinical and electrophysiological findings. He had a high titre of anti-GM1 IgG antibodies and cytoalbuminologic dissociation and was responsive to intravenous immunoglobulins. Investigations and three years of follow-up excluded mimics of GBS. Tendon areflexia has recently been challenged as a mandatory diagnostic criterion in GBS; likewise marked and persistent motor asymmetry does not exclude the diagnosis of GBS.