A comparison of Paraghurt tablets (freeze-dried culture of Streptococcus faecium) and placebo was carried out in patients with irritable bowel syndrome in a double-blind trial in Danish general practices. Fifty-four patients (42 females and 12 males) with an average duration of the disease of seven years were treated for four weeks. The clinical symptoms were registered prior to the treatment and after two and four weeks. The clinical effect was assessed according to changes in number of abdominal symptoms, the patients' registrations on rating scales, and the physicians' overall estimations. According to all three parameters a markedly better effect of Paraghurt was seen. Thus, after four weeks 81% of the Paraghurt- and 41% of the placebo-treated patients had improved according to the physicians' overall assessment (p = 0.002). The result of the trial suggests that Paraghurt is a valuable alternative in the treatment of irritable bowel syndrome.