Intravoxel incoherent motion (IVIM) can be seen as subfield of diffusion MRI. It allows tissue microcirculation (perfusion) to be investigated in addition to tissue microstructure (from molecular diffusion). IVIM MRI does not require the application of contrast agents; therefore, it serves as an interesting alternative to perfusion MRI in pediatric patients or in patients with contraindications for contrast agents. This chapter points out the technical background of IVIM including its physical principles, the processing of IVIM data, and the comparison to classical perfusion imaging techniques. Clinical applications of IVIM are given among others for ischemic stroke imaging, brain tumor imaging, and imaging of head and neck pathologies.