SUMMARYFour restriction enzymes (AluI, HhaI, MspI and RsaI), either individually or in combination, were used in terminal restriction fragment length polymorphism (T-RFLP) analysis to: (i) characterize the chicken intestinal bacterial community; and (ii) tentatively identify intestinal bacterial groups related with increased performance parameters in broiler chickens. Balanced commercial diets free of any feed antibiotics were offered to broilers assigned randomly to one of the five dietary treatments: control (C) (commercial diet with no additive), inulin (I), fructose caramel, propyl propane thiosulphonate (PTS-O)-45 and PTS-O-90. Except for the inulin-supplemented diet, multivariate statistical analysis of T-RFLP profiles based on individual enzymes or their combinations showed that the caecal bacterial community composition was significantly different among diets, particularly between the control and the supplemented diets. Individual RsaI and the combination AluI + RsaI proved to be the most useful to discriminate between dietary treatments. Clostridiaceae 1, Lachnospiraceae, Ruminococcaceae and Micrococcaceae were tentatively identified as those families most likely to be implicated in defining the caecal microbiota composition of growing broiler chickens, and also as those most closely related with differences in productive parameters.