Surgery was undertaken on 32 chronic subdural hematomas in a series of 28 patients who had preoperatively undergone delayed contrast-enhanced computed tomography (DCECT). Time-density curves on DCECT and iodine concentrations of subdural specimens revealed that chronic subdural hematomas, regardless of density, were significantly enhanced by the entrance of intravascular contrast medium into the interior of hematomas. The ingress of intravascular contrast medium into the interior of the hematomas was chemically proven and might result from a complex transcapillary shift.