Five purified concentrates – Nanotiv (Kabi Pharmacia), Immunine (Immuno), Factor IX VHP (Biotransfusion), Alphanine (Alpha Therapeutic Corporation), and Mononine (Armour Pharmaceutical Company) – were characterized biochemically and their in vivo pharmacokinetic and thrombogenic properties evaluated. The results were compared with those for two prothrombin complex concentrates (PCCs): Preconativ (Kabi Pharmacia) and Prothromplex TIM4 (Immuno). The measured values for factor IX coagulant activity (FIX:C) generally agreed with the manufacturers’ labeled values. The purified concentrates were virtually devoid of other vitamin K-dependent coagulation factors, the inhibitor proteins C and S, and either fibrinogen, fibronectin, or immunoglobulins. Indicators of thrombin generation (i.e., prothrombin fragments F1+2 and thrombin-antithrombin complex) were present in varying amounts in all preparations. The level of specific activity in the purified concentrates exceeded that in the PCCs by a factor of 50- to 100-fold. Pharmacokinetic variables were studied in severe hemophilia B patients: Nanotiv was compared with Preconativ; Immunine was compared with Prothromplex TIM4 in crossover studies; and Mononine was tested in a single-drug study. No differences were apparent between Nanotiv, Preconativ, and Mononine, but recovery rates were lower, clearance rates higher, and FIX:C half-life shorter for Immunine and Prothromplex TIM4, although the disparate results might have been attributable to methodologic differences. Purified factor IX concentrates were used successfully as cover for surgery and in immune tolerance induction without observable adverse effects.