Irritable Bowel Syndrome (IBS) may be diagnosed on the presence of symptoms, according to Rome II criteria, [corrected] and some studies have shown that abnormal colonic fermentation may be an important factor in the development of symptoms in some patients with IBS. Since the fermentation [corrected] of substrates by the intestinal flora may play a key role in the use of probiotics in the treatment of IBS, seventy [corrected] patients (31 [corrected] males, 39 [corrected] females), mean age 40 years (range = 26-64 years) with IBS, according to Rome II criteria, were enrolled into the study after informed consensus. Patients were randomly assigned to receive for 4 weeks [corrected] either the active preparation containing Lactobacillus plantarum LP 01 [corrected] and Bifidobacterium breve BR 03 [corrected] or Lactobacillus plantarum LP 01 and Lactobacillus acidophilus LA 02, all strains at concentrations of 5 x 10(9) CFU/g) [corrected] or placebo powder containing starch identical to the study product [corrected] To evaluate treatment efficacy two different scores were considered [corrected] Pain score in different abdominal locations after treatment decreased in probiotics groups A and B 42% and 49% versus 25% [corrected] (P < 0.05) in [corrected] placebo group after 14 days and 45% and 49% versus 29.5% [corrected] (P < 0.001) after 28 days. The severity score of characteristic IBD symptoms significantly decreased in probiotic groups A and B [corrected] versus placebo group after 14 days, 49.3% and 55.6% [corrected] versus 8% [corrected] (P < 0.001), and these data were confirmed after 28 days (56% and 55.6% versus 14.4% [corrected] P < 0.001). In conclusion, short-term therapy with Lactobacillus plantarum LP 01 and Bifidobacterium breve BR 03 or Lactobacillus plantarum LP 01 and Lactobacillus acidophilus LA 02 [corrected] may be considered a promising approach for IBS therapy [corrected]