This paper reviews the use of extracorporeal immunoadsorption with immobilized Staphylococcal Protein A in attempts to lower the inhibitor titer in 22 patients with either congenital hemophilia or with acquired inhibitors. Eighty-five immunoadsorption procedures were performed at 13 locations in the United States between June, 1987 and February, 1990. In general, immunoadsorption was shown to efficiently remove IgG and, in eight congenital hemophilia patients, it also produced a clinically significant lowering of inhibitors allowing effective conventional factor replacement therapy. Three of thirteen congenital hemophilia patients treated received factor concentrate prior to immunoadsorption and were anamnestic at the time of treatment. Although they experienced substantial lowering of their inhibitor titers, it was not sufficient to allow effective factor replacement. The effectiveness of immunoadsorption therapy in the 9 patients with acquired inhibitors was more difficult to evaluate due to the wide variety of concomitant medications which were employed, although in several patients serious bleeding episodes were substantially improved (or halted) following immunoadsorption. Side effects associated with immunoadsorption were slight. These findings suggest that immunoadsorption can be a significant benefit to patients with inhibitors, particularly if it is instituted prior to factor administration.