Aims: To investigate the effect of prolonged consumption of a synbiotic milk (Synbiotic) containing Lactobacillus acidophilus (strain 74-2, 10(7) CFU ml(-1)), Bifidobacterium lactis (strain 420, 10(7) CFU ml(-1)) and 2% inulin on colonic ecosystem in healthy humans. Methods and Results: A group of 26 healthy subjects, aged 22-47 years, participated in a 6-week placebo-controlled dietary intervention study. After a 2- week baseline period, in which all volunteers consumed 500 ml day(-1) of 2% skimmed milk (Placebo), the study was designed as a randomized, double-blind, two-armed parallel study in which 4-week consumption of 500 ml day portions of Synbiotic or Placebo were compared. Faecal microbial counts, pH, L-lactic acid and bile acid concentrations were assessed before and after the intervention. Synbiotic consumption significantly decreased faecal dry weight (P < 0.01) and L-lactic acid (P < 0.05) concentration, while significantly increased faecal bifidobacteria. (P < 0.05) and lactobacilli (P < 0.01) counts. Conclusion: The tested synbiotic milk showed its synbiotic nature by enhancing the growth of bifidobacteria and lactobacilli. Significance and Impact of the Study: Scientific support to functional effect of a synbiotic milk.