A process for the specific adsorption of heparin and other heparin-like substances which comprises flowing a buffered solution of whole blood, from which corpuscular blood constituents have been removed, plasma and/or solutions containing whole blood or plasma through an adsorber capsule containing a medium that adsorbs heparin and other heparin-like substances at an acid pH, preferably in the range of 4.0 to 5.5. Preferably, the process is carried out in a closed, extracorporeal circulation and the medium possesses anion exchange resin properties.