The efficacy of a chromatographic procedure based on hydrophobic interaction chromatography to remove non-A, non-B (NANB) infection from a concentrate of coagulation factors II, VII, IX and X (Preconativ, KabiVitrum AB) was evaluated in chimpanzees. For this purpose, NANB infective human plasma (H-strain) was deliberately added to a solution of Preconativ (45 IU factor IX:C/ml) to reach a titre of NANB virus of greater than or equal to 10(2) chimpanzee infectious doses (CID)/ml. The NANB-contaminated preparation was chromatographed on octanohydrazide-Sepharose 4B at a high salt concentration. Groups of 2 chimpanzees were each inoculated intravenously with 45 IU factor IX:C of Preconative before and after this virus adsorption chromatographic step. The experimental animals remained free of any serological and biochemical evidence of hepatitis during a 12-month follow-up period. One of the two control animals developed clear evidence of NANB hepatitis.