In a sheep which was euthanased because of severe emaciation and weakness, slight thickening of the ileum was seen grossly. Microscopically there was a granulomatous ileitis with obliterative lymphangitis and lymphangiectasis. Granulomatous lesions were also present in the liver and some mesenteric lymph nodes. Large numbers of acid-fast bacilli were present within epithelioid macrophages in the lamina propria of the ileum. Although the identity of the Mycobacterium spp. involved was not established, the possibility of paratuberculosis is discussed. The apparent rarity of this disease in sheep in South Africa is considered. Particular attention is drawn to the absence of diarrhoea in this case, to the slightness of the gross changes and to the importance of submitting material for mycobacterial culture.