Background: It is well documented that fermentation of carbohydrates that escape digestion exert several effects supposed to be beneficial for (colonic) health, including an increase in stool volume, a shorter intestinal transit time, production of short chain fatty acids and a decrease of colonic pH (Kritchevsky 1988). NUTRIOSE®FB is a dextrin that is not completely hydrolysed and absorbed in the small intestine, due to many α-1.6 linkages and the presence of non-digestible glucoside linkages (e. g. α-1.2 and α-1.3). To be beneficial for 'colonic' health effective NUTRIOSE®FB must reach the cecum in some form. Aim of the study: To estimate how much non digested NUTRIOSE®FB is fermented and to determine the fibrelike effect of the wheat dextrin NUTRIOSE ®FB by analysing enzymatic activity in faeces. Methods: In a randomized, double-blind,multiple dose, placebo-controlled, combined cross-over and parallel trial, 20 healthy men (age 31.7 ± 9.1 yrs; BMI 24.5 ± 2.9 kg •m-2 received different treatments. One group of ten subjects consumed on top of their diet 10, 30 and 60 g daily of NUTRIOSE ®FB or maltodextrin (placebo). The other group of 10 subjects consumed 15, 45 and 80 g daily. Each dose was consumed for 7 days. On the last two days of each of the 7-day period, faeces were collected in which the enzymatic activity and NUTRIOSE®FB residue were analysed. Results: As expected, the faecal residue of NUTRIOSE®FB non-linearly increased with the dose of NUTRIOSE®FB to approximately 13% of 80 g/d. Compared with the placebo, 30, 45, 60 and 80 g/d of NUTRIOSE®FB increased the concentration of α-glucosidase significantly. All daily doses of NUTRIOSE®FB (10 g/d to 80 g/d) led to significant changes in concentration of β-glucosidase. Conclusions: The small amount of the residue of NUTRIOSE®FB in the faeces suggests that approximately 87% or more of NUTRIOSE®FB is digested or fermented in the gastrointestinal tract. Fermentation of NUTRIOSE®FB led to an increased faecal concentration of α- and β-glucosidase. © Steinkopff Verlag 2005.