To detect and characterize deep vein thrombus (DVT), we performed diffusion weighted magnetic resonance imaging (MRI) in 8 patients and a rabbit model of DVT. All patients were detected DVT as high or mixed high and iso signal intensity on diffusion weighted MRI. The rabbit venous thrombi showed high signal intensity on diffusion weighted MRI at 4 hours, or mixed iso to high and low signal intensity at 1, 2, 3 weeks. The signal intensity was positively correlated with erythrocyte contents. Diffusion weighted MRI can detect DVT and high signal intensity on the sequence may reflect early phase of DVT.