OBJECTIVE: The aim of this study was to evaluate the effect of the alcohol consumption on the periodontal bone support (PBS) in experimental periodontitis in rats. MATERIALS AND METHODS: Sixty-three male rats were divided into seven groups: G1 (control); G2 (10% ethanol); G3 (nutritional control of G2); G4 (20% ethanol); G5 (nutritional control of G4); G6 (30% ethanol) and G7 (nutritional control of G6). The groups G3, G5 and G7 received controlled diets with equivalent caloric amounts to those consumed in G2, G4 and G6 respectively, with the ethanol replaced by sucrose. After anesthesia, ligatures were installed around the mandibular first molar, leaving the contralateral teeth unligated. After 8 weeks, the rats were killed and their mandibles were radiographed to measure the percentage of PBS on the distal aspect. RESULTS: The intragroup analyses showed that presence of ligatures induced periodontitis (p<0.05). Unligated groups did not show significant differences among the percentages of PBS (p=0.1969). However, in ligated groups the rats that received alcohol (G2:48.71%+/-3.88; G4:47.66%+/-2.54; G6:47.32%+/-3.24) and the nutritional control group associated with a high concentration of ethanol (G7:47.40%+/-3.24) presented a significantly lower percentage of PBS than the other groups (G1:52.40%+/-2.75; G3:52.83%+/-2.41; G5:50.85%+/-4.14). CONCLUSIONS: These results demonstrated that alcohol consumption in rats may result in a direct effect on alveolar bone loss and increased development of periodontitis. In addition, they suggest that heavy caloric consumption of ethanol may also present an indirect effect on periodontal tissue as a consequence of malnutrition.