We analysed data obtained from 27 out of a group of 147 patients with Guillain-Barré syndrome, who did not have sensory loss during a follow-up period of 6 months (motor Guillain-Barré syndrome). These patients had a distinctive clinical pattern compared with the other 120 Guillain-Barré syndrome patients. The clinical course was marked by a more rapid onset of weakness (3.9 versus 6.1 days, P = 0.002), an earlier nadir (6.3 versus 9.1 days, P < 0.001), an initially predominant distal weakness (67% versus 27%, P < 0.001), sparing of the cranial nerves (26% versus 68%, P < 0.001) and the disease was more often preceded by a gastro-intestinal illness (41% versus 13%, P = 0.001) often caused by a Campylobacter jejuni infection (67% versus 28% in the other Guillain-Barré syndrome patients, P < 0.001). High titres of anti-GM1 antibodies were also significantly more common in motor Guillain-Barré syndrome patients (42% versus 5%, P < 0.001). Electromyographic data of the motor Guillain-Barré syndrome patients at nadir revealed little or no evidence for demyelination. Abundant denervation activity was present in half of the patients. The response to immune globulin treatment was good but with plasma exchange significantly fewer motor Guillain-Barré syndrome patients reached the stage of independent locomotion after a follow-up period of 6 months especially if the acute motor neuropathy occurred after a C.jejuni infection.(ABSTRACT TRUNCATED AT 250 WORDS)