Until the end of 1974, heparin was not added to factor IX concentrates. The Task Force on Clinical Use of Factor IX Concentrates recommended to the International Committee on Thrombosis and Hemostasis in Basel [Switzerland] in September, 1974 that heparin be added. Heparin (1 unit/10 units of factor) is now added. However, over 80% of the concentrates did not contain heparin. More than 15 million units have been used clinically to treat hemarthroses in over 300 patients; many are on home therapy and some self-inject. More than 90 dental operations were performed. Major surgical operations were carried out in 45 instances in 40 patients. One patient received 325,000 units over 15 mo. without clinical complications. In only 2 of these 45 operations was there clinical evidence suggestive of thrombosis. The observations of Lane, Rizza and Snape (1975) on the use of factor IX type DE in the treatment of Christmas disease are extended. The material was also used to treat patients requiring rapid reversal of anticoagulant therapy and patients with liver disease requiring liver biopsy; no adverse effects were reported.