A simple procedure is described for the large-scale absorption on to DEAEcellulose of coagulation factors II, IX and X from citrated, factor VIII-depleted plasma. The coagulation factors are eluted frontally from the exchanger in a high yield and in a form suitable for therapeutic use, without further fractionation. The lyophilised concentrate is very stable without the addition of heparin and, when redissolved to isoosmolar solution, contains approximately 30 U/ml factors II, IX and X, 250-300 times purified from the starting plasma. The effectiveness of the concentrate in the treatment of haemophilia B is discussed.