Probiotics have been used with apparent success for several gut disorders, so it is not surprising they have been tried in the treatment of irritable bowel syndrome (IBS). However, the pathogenesis of this disease is unknown, and opinions about how probiotics might work are speculative. Nevertheless, two small trials suggest they might benefit patients with IBS, particularly those suffering from pain and bloating. This possibility deserves further study. It is important though, that future trials employ criteria-identified subjects, be sufficiently powered and strictly double blind, and select a suitable outcome measure. Until state-of-the-art trials of probiotics are available, their use should remain in the experimental arena.