A process for reduction and/or removal of FXI and FXIa from a source solution containing said coagulation factors and as main components immunoglobulins comprising the following steps: a) contacting the FXI and/or FXIa containing solution with an affinity chromatographic gel wherein heparin or heparan is linked to the matrix material; b) allowing adsorption of FXI and/or FXIa and c) separation of the liquid deprived of FXI and/or FXIa from the adsorption media.