Lecture about ultrafiltration to concentrate extracellular vesicles (EVs) by Joel Nordin as part of the third massive online open course (MOOC) of the International Society for Extracellular Vesicles (ISEV). The lecture covers the basic principles of ultrafiltration, including dead-end filtration and tangential flow filtration (TFF), the performance of ultrafiltration methods in terms of EV recovery and enrichment, practical information, do’s and don’ts as well as examples.