Deep vein thrombus (DVT) is gradually replaced by fibrous tissue, and is called as organizing reaction. We examined magnetic resonance image (MRI) findings of the organizing DVT in vitro using a 1.5T MR system in autopsy cases with DVT. The organizing area of DVT showed low signal intensity (SI) on T1 weighted images, in contrast to high SI on T1 weighted images in non-organizing area. Both areas showed iso to low SI on T2 weighted image. T1 SI positively correlated with the erythrocyte content in the thrombus. MRI could discriminate organizing from non-organizing area in DVT.