A common problem in rabbits is the occurrence of digestive disorders just after weaning. This problem is associated with instability of the cecal microflora, and characterized by diarrhea, loss of appetite and increased mortality. The supplementation of diets with fructo-oligosaccharides (FOS) can improve animal’s health and performances by selec- tive stimulation of beneficial endogenous bacteria in the cecum. A trial with the objective of evaluating the effects of FOS on growth performances and intestinal morphometry of growing rabbits was conducted. A total of 144 mixed-sex growing rabbits (817±35 g) were submitted from 35 to 70 days of age to 2 experimental treatments. The 2 treatments were applied to a common basal diet as follow: 1) Control (no FOS); 2) FOS (0.36 g.kg -1 diet). Experimental diets were offered ad libitum. No statistical differences on mortality and diarrhea frequency were observed during the essay. The Control and FOS rabbits had similar live weights at 35 (821 vs. 812 g), 49 (1107 vs. 1146 g) and 70 days (2223 vs. 2234 g), weight gain and feed intake. However, the feed efficiency on the growing period tended to be higher with FOS diet (0.274 vs. 0.304; P=0,056). No significant effects are observed on morbidity and mortality. FOS did not affect the weights of liver, cecum, small intestine and stomach. Also the ileal villi measurements did not show differences between treatments. Results of this study suggest that FOS increase feed efficiency and have negligible effects on growth performance and microbial activity. Key words: fructo-oligossacarides, rabbit, growth, microbial activity, villi measurement.