Paratuberculose enteritis is an infectious and contagious chronic disease of the rumiants. It is characterised by periodic diarrhoea and progressive emaciation and loss of condition, intestinal ileitis and oedematous mucosa with cirumvolutions. The disease is caused by Mycobacterium avium subsp. paratuberculosis. Crohn's disease or inflammatory bowel disease has identical characterization with ileitis, colitis with oedematous state and enlarged intestinal mucosa. Iflammatory infiltration of the intestinal mucosa has a transmural character, affecting the submucosa. The similarity between Crohn's disease and Johne's disease is the reason for considering an identical etiology for both diseases, but in the 75 years of the natural history of Crohn's disease it has been impossible to demonstrate this hypothesis. However, actually the predominant idea is that Mycobacterium avium subsp. paratuberculosis is frequently present in patients with Crohn's disease. This has been demonstrated by hemocultures, PCR and in situ hybridization.