During a 9-year period, 16 patients with a delay in diagnosis of an injury to the diaphragm after a penetrating wound were treated. The left hemidiaphragm was involved in 15 of 16 patients, and the delay in diagnosis from the time of arrival in the emergency center immediately after injury ranged from 16 hours to 14 years. In the patients in the Acute Group (delay of hours to days), three patients had diaphragmatic defects missed at the time of laparotomy, three patients had chest X-rays not immediately suggestive of diaphragmatic defects, two patients had false-negative lavages, and one patient treated elsewhere did not have a chest X-ray in the emergency room. In the patients in the Chronic Group (hernias presenting months to years after injury), four of seven patients had misreading of a recent chest X-ray or failure to have a chest X-ray performed during numerous return visits to the emergency center. Despite a variety of diagnostic maneuvers, these defects and hernias continue to be diagnosed after a delay. Careful review of early and late followup chest X-rays appears to be the easiest mechanism to avoid significant delays in diagnosis.