Based on culture and serological evidence, a strong association between Campylobacter jejuni infection and Gullain-Barré syndrome (GBS) has been established. However, culture underestimates C. jejuni infection in GBS and the specificity of serology remains uncertain. Thus, a direct sensitive detection method for recent C. jejuni infection is required. We used the PCR technique in GBS patients to assess its role in the diagnosis of C. jejuni infection. From June 2001 to March 2003, stool specimens from 42 patients with GBS and an equal number of age- and gender-matched healthy controls were analysed for C. jejuni infection by culture and PCR. Gullain-Barré syndrome subtypes were classified by clinical and electrophysiological studies. Of the GBS patients, two (4.8%) and eight (19%) were positive by culture and PCR, respectively, and the difference was significant (P < 0.05). None of the controls were positive for C. jejuni by culture or PCR. All C. jejuni-positive GBS patients had axonal degeneration with or without sensory involvement. The incidence of C. jejuni-associated GBS cases was more frequent during summer than winter (7/19, 36.8% vs. 1/23, 4.3%, P < 0.01). Polymerase chain reaction appears to be a sensitive tool to detect preceding C. jejuni infection in GBS patients.