[en] A sequential MR scan was performed on 21 patients with intracranial hematoma, and simultaneously the T₁ values of the hematomas were calculated. The T₁ value of a hematoma was found to be longer than that of the white matter in the acute phase, but it soon becomes as short as that of the white matter (7 - 10 day after). After several days, the T₁ value again gradually becomes longer. In the experiment, 30 ml of fresh blood (15 samples) were stored at room temperature, and a sequential MR scan and the calculation of the T₁ were performed over a period of 20 days. In vitro, most of the T₁ values were long, but there was much variation on the first day. A shortening of the T₁ was observed as well in vivo, and after this shortening, no prolongation of the T₁ was observed. Perhaps the shortening of T₁ was caused by the denaturation of the hemoglobin to methemoglobin and by the coagulation of the blood. The lysis and absorption of the hematoma may, on the other hand, cause the prolongation of the T₁ in vitro. For the diagnosis of intracranial hematoma, CT was found to be a method superior to MRI, especially in the acute phase. However, MRI gives us more information about hematoma (concerning the denaturation of the hemoglobin to methemoglobin, the lysis and absorption of the hematoma, the range of hemorrhagic tissue and edema, etc.) than does CT. An IR (T₁-weighted) image shows a good contrast between the hematoma and the surrounding tissue (hemorrhagic tissue, edema) in the early phase. On the other hand, the SE (T₂-weighted) image informs us of the lesion when the hematoma is low ∼ isodense on the CT in the chronic phase. (author)