The Guillain-Barré syndrome is an inflammatory demyelinating polyneuropathy with an acute or subacute onset. The current case-control study was performed to investigate the possible role of drugs and other determinants in the causation of the Guillain-Barré syndrome. Patients were included as cases if they fulfilled the criteria for acute Guillain-Barré syndrome and were unable to walk 10 m independently and had been admitted to the hospital within 2 weeks of onset of the neuropathy. For every case, two controls without the disease were obtained from the general practitioner (GP) of the patient with Guillain-Barré syndrome. Controls had the same type of health care insurance, were of the same gender and age (within 5 years), and resident in the same area. By telephone, the GPs of the patients with Guillain-Barré syndrome were interviewed. There were 71 female and 75 male cases and 142 female and 149 male controls. Significantly more cases than controls had been prescribed drugs in the 3 months prior to the index date and also diagnoses or symptoms in cases were more common. Case patients used significantly more frequently antipropulsives (loperamide), penicillins (amoxicillin with or without clavulanic acid) and vaccines. Female controls used significantly more often oral contraceptives. More cases than controls suffered from infections of the respiratory, gastrointestinal or urinary tract prior to the onset of neurological symptoms. In a logistic regression analysis, symptoms concerning the gastrointestinal and respiratory system were strongly associated with the Guillain-Barré syndrome. The use of oral contraceptives was significantly lower in female cases which could be compatible with the hypothesis that these drugs are protective.