SummaryActivated Hageman factor has been isolated from human granulocytes, utilizing aluminium hydroxide gel, diatomaceous earth, CM-cellulose. The preparation was applied on the column prepared from DEAE-Sephadex A-50. Two peaks with Hageman activity were obtained. The product was purified 4162-18750-fold as measured by the method of Schoenmakers et al.The preparation was devoid of factor I, II, III, V, VIII, IX and plasminogen. Some relationship between granulocyte and plasma Hageman factor are briefly discussed.