Objective: The aim of this observational and analytical case-control study was to verify the association between inflammatory bowel disease and periodontal disease. Methods: The sample was selected among the patients from the General Gastroenterology and Inflammatory Disease Clinic of the Hospital Garcia de Orta, Almada, Portugal, with a diagnosis of Crohn's disease or ulcerative colitis who have agreed to participate in this study. For each patient we determined the values of the Community Periodontal Index and the Simplified Oral Hygiene Index. We also obtained data regarding oral hygiene habits, smoking habits, drug therapy, duration and activity of inflammatory bowel disease. The control group consisted of healthy individuals accompanying the study group patients to their appointments. Results: The Community Periodontal Index (0-5) showed values of 2.0±1.07 for the control group and 2.8±0.98 for the study group. This difference was statistically significant (p0.0001), showing a higher severity of periodontal disease in these patients. The periodontal status deteriorated in the course of the disease, but not in a statistically significant way. Conclusions: There was a positive association between periodontal disease and inflammatory bowel disease, since the patients suffering from this disease showed more severe periodontal affections when compared with the controls. Keywords: Inflammatory Bowel Disease, Crohn's Disease, Ulcerative Colitis, Periodontal Disease