A unique finding of an extraskeletal pseudomalignant osseous lesion of the mesentery and omentum was detected in a 63-yr-old insulin-dependent diabetic man, following aortic bifemoral bypass and two subsequent laparotomies at 2-wk intervals for intractable intestinal obstruction. An analogy is made to myositis ossificans and fasciitis ossificans. The histogenesis of new bone formation from connective tissue following chemical or physical stimuli supports a metaplastic mechanism. Our review of the literature reveals no prior report of a similar case.