Homogeneous high density (of biconvex shape)has been the CT hallmark of epidural hematomas. High resolu-tion CT demonstrates the structural detail of hematomas and as a result all the hematomas are no longer homogeneous. Authors reviewed CT findings of 27 lesions os epidural hematomas within 72 hours of head injury and frouped into 4 types according to the density homogeneity : type 1: well-defined low density area within hematoma type 2: ill-defined low density area within hematom (laminar, hole, or irregular) type 3: homogeneous high density hematoma with or without internal mottling type 4: marginal low density area along hematoma Types and time interval between head injury and CT examination are well correlated; The mean time dura-tions of each type are 2hr, 7.6hr, 15hr, and 53 hr in order.The lucency in type 1 represents active bleeding from meningeal artery or dural sinus. The inhomogeneity in type 2 is due to liquid blood within clots. The fomogeneity in type 3 means complete clot formation. the marginal low density in type 4 reflects retraction of blood clot.