Free bowel perforation is a relatively infrequent complication of Crohn's disease. It may present during the evolution of the disease or, occasionally, in the onset of the same and may involve the small intestine or colon. We herein present 4 cases, three of ileal localization and one of colonic localization. In one of the 3 former cases and the latter case perforation took place prior to diagnosis of the disease. Review of the literature was performed with respect to the frequency, pathogenesis and characteristics of this complication and the importance of determined diagnostic techniques such as echography and CAT in addition to the most adequate treatment are commented upon.