Diffusion-weighted imaging (DWI) represents a relatively novel magnetic resonance imaging (MRI) technique in which image contrast is related to differences in translational motion of water molecules within the tissue, rather than to differences in total water content. The rate of water motion is characterized by the apparent diffusion coefficient. In addition, full tensor DWI (diffusion tensor imaging, DT-MRI) samples the full diffusion tensor and therefore allows estimation of isotropic and anisotropic diffusion. The degree of anisotropic diffusion is thought to be determined by the local tissue characteristics or tissue architecture and can be quantified by DT-MRI. DWI has proven its clinical effectiveness in the early detection of acute cerebral ischemia. Multiple reports have discussed the value of DWI in a wide variety of other diseases of the central nervous system. DT-MRI appears to be especially promising in the evaluation of diseases that affect the integrity of white matter, in particular of white matter tracts. Herein, the current applications of DWI in clinical neurology are reviewed, with special attention to applications of DT-MRI.