Abstract: Coagulation control compositions suitable for use in connection with PT and/or APTT assays are disclosed along with their methods of preparation and methods of use. Preferred coagulation controls comprise plasma and an anticoagulant having activity for enhancing the activity of antithrombin III (ATIII) or of heparin co-factor II (HCII) against thrombin or against a clotting factor selected from the group consisting of factors IXa, Xa and XIa. The anticoagulant is preferably a glycosaminoglycan such as heparin, a heparin derivative or a heparin analog. The anticoagulant is preferably combined with (1) an abnormal plasma (e.g. activated plasma or factor-deficient plasma) and/or (2) a primate plasma (e.g. human plasma), and a non-primate mammalian plasma (e.g. bovine plasma). In the latter case, the non-primate mammalian plasma is preferably present in the coagulation control composition in an amount of not more than about 12% by volume, relative to total volume.