Heat treatment of lyophilized factor VIII and factor IX concentrates has been found to eliminate HIV virus infectivity in plasma-derived products. Pasteurization of factor VIII in solution has recently been used to reduce the risk of hepatitis transmission in concentrates prepared by standard fractionation methods. This report presents early experience with factor VIIIC prepared by monoclonal antibody immunoaffinity chromatography following pasteurization of the factor VIIIC/von Willebrand factor complex (Monoclate-P). Twelve patients were treated in three centers with Monoclate-P. Recovery and survival of factor VIII clotting activity were determined and patients were closely monitored for infusion safety. The mean half-life was 14.2 +/- 5.0 while recovery in predicted plasma volume was 72 +/- 12% corresponding to a response of 1.99 +/- 0.66 U/dL for every U/kg administered. These values are very similar to those found for Monoclate in previous studies indicating that pasteurized factor VIIIC purified by immunoaffinity chromatography retains satisfactory pharmacokinetic properties with an added margin of viral safety.