Our findings imply that routine intraoperative radiographic screening in selected, high-risk categories of operations could prove to be a useful measure for detecting foreign bodies that have been inadvertently left behind. On the basis of previous estimates that such incidents occur in 1 in 1500 operations involving an open abdomen or chest 6 and our findings that emergency status applied to one third of patients with retained objects and just 7 percent of controls, we estimate that 300 radiographs would be needed to detect 1 retained foreign body. A prospective study would be needed to test such an estimate. However, given costs of more than $50,000 per case for malpractice-claims expenses alone, a $100 plain film could prove a cost-effective intervention.