In a first experiment, 800 one-d-old male Ross 308 chicks were randomly allocated to 40 replicate pens with 20 chicks per pen. Five inclusion levels of clove were tested: 0, 100, 200, 1000, and 2500 mg/kg. Treatments were fed from 0 to 35 d of age. Feed to gain ratio was modified with clove inclusion showing a cubic effect (P<0.05). Levels of 100 and 200 mg/kg showed the lower feed to gain ratio. At 21 and 35 d of age, 2 broiler chickens per pen were selected from diets containing 0 and 100 mg/kg of clove and samples from ileal content and tissue were collected to evaluate microbiology and intestinal morphology. Enterobacteriaceae counts were not affected by clove supplementation at 21 d of age, but the number of Lactobacillus was increased compared to the control diet (9.62 vs. 9.18 log cfu/g digesta; P<0.05). Moreover, clove inclusion increased the number of intraepithelial lymphocytes (1.55 vs. 2.22 lymphocytes/100 enterocytes; P<0.01) and lamina propria cell density (5.98 vs. 6.84 cells/1000 micro-m2; P<0.05) in the intestinal epithelium of 21 d-old broiler chickens. In a second experiment, 150 d-old male Ross 308 broiler chickens were randomly allocated to 30 cages with 5 broiler chickens per pen. From 19 to 21 d of age, feed intake and total excreta from each cage were recorded and sampled daily and the effect of the same 5 levels of clove on DM and OM digestibility was assessed but, no differences were observed. Clove at doses of 100–200 mg/kg seem to improve feed efficiency. Interesting changes in intestinal microbiota and epithelium were observed but further studies are required to clarify the mode of action of clove in broiler chickens.