To try to define the significance of disseminated intravascular coagulation (DIC) in head-injured patients, we correlated clinical, laboratory, and pathological findings in 16 patients with head injury as their main problem who had DIC, who died within 4 days of injury, and who were examined postmortem. Patients were ranked according to the number of abnormal laboratory screening tests for DIC and the severity of these abnormalities. The most frequently abnormal laboratory tests were the fibrinogen degradation products and fibrinogen, followed in order by the activated partial thromboplastin time, prothrombin time, and thrombin time. The platelet count was the least abnormal value. The patients with the fewest abnormalities had the least abnormal computed tomographic scans. Autopsy reports revealed necrosis and bleeding in the brain and in a number of other organs, particularly the lungs. Microthrombi were not reported in the original autopsy reports. However, when these cases were reevaluated and their slides were stained with an immunoperoxidase technique using rabbit anti-human fibrinogen antiserum, microthrombi were seen frequently. Large microthrombi were more common in patients who had died within less than 24 hours, suggesting a relationship to death or to less time for lysis. In order of frequency, the brain/spinal cord, liver, lungs, kidneys, and pancreas were most commonly affected, and the liver, pituitary gland, pancreas, thymus, brain/spinal cord, large intestine, kidneys, and lungs had the greatest density of microthrombi. Pulmonary dysfunction had been a frequent problem in these patients, which may have been related to the high incidence of microthrombi and bleeding found in the lungs.(ABSTRACT TRUNCATED AT 250 WORDS)