Two cases of jejunal diverticulosis associated with intrinsic factor deficiency are reported. One case had megaloblastic anaemia and full correction of 58Co vitamin B12 absorption was achieved by broad spectrum antibiotic therapy alone. The second case had intrinsic factor deficiency and full correction of 58Co vitamin B12 absorption was achieved by the addition of oral intrinsic factor alone. The variable contribution made to the development of vitamin B12 deficiency in jejunal diverticulosis by intrinsic factor deficiency and bacterial colonisation of the small intestine is discussed.