[en] It is known that the signal intensity of MR of the hemorrhage or hematoma varies with the age of the lesion. The mechanism causing the various MR intensity if mainly related to change of T1 and T2 relaxation times (T1 and T2) of blood resulting from physiochemical changes in the extravasated blood. It has been suggested that this change of relaxation times of blood is largely due to the conversion of hemoglobin (Hb) to the Methemoglobin (met-Hb) form, a substance with a relaxing effect on nuclear spins. The purpose of this study was to present the measured values of T1 and T2 relaxation times of blood in magnetic field strength of 2.0 Tesla (T), and to evaluate the relation of MR signal intensity, T1 and T2 values in high-field MR canner, with Hb, met-Hb and the age of blood. A total of 31 samples of whole blood were examined in vitro on 2.0T MR scanner at Korea Advanced Institute of Science and Technology (KAIST). The T1 and T2 relaxation times were measured with the MR images of all blood samples, and correlated with the concentrations of Hb, met-Hb and lapse of the time of all blood samples. The results were as follows: 1. T1 values ranged from 1305 to 2625 msec in supernates (plasma) and 603 to 1655 msec in precipitates packed cells). T2 values ranged from 130 to 451 msec in supernates and 55 to 152 msec in precipitates. 2. In supernates (Hb, 0-9.8 g%), the higher Hb concentration was, the shorter T1 relaxation time was (ρ < 0.01), but there was no correlation between T1 values and Hb concentration in precipitates (Hb, 11.1-27.2 g%) (ρ > 0.05). In both supernates (met-Hb, 0-0.1 g%) and precipitates (met-Hb, 0-4.6 g%), the higher the met-Hb concentration was, the shorter T1 relaxation time was (ρ < 0.01). The T1 values of 4 week, 6 week and 8 week bloods were lower than those of 2 week or less in both supernates and precipitates. 3. In supernates (Hb, 0-9.8 %), the higher Hb concentration was, the shorter T2 relaxation time was (ρ > 0.01), while T2 relaxation times were relatively constant regardless of the change of Hb concentrations in precipitates (Hb, 11.1-27.8 g%) without significant correlation. There was no correlation between T2 values and met-Hb concentrations in both supernates and precipitates. The T2 values of the supernates and the precipitates showed no significant change with lapse of time. It is suggested that these results may help to interprete more accurately the image of hematoma in high-field MR scanner. But further investigation and experience with MR is needed to allow diagnostic radiologists to determine more definitively the multifarious phases of extravascular blood, because in vitro study may not be directly correlated with that in vivo status