the initial testing of the safety of a cellulose-heparinase hollow fiber device was assessed with respect to physical properties and in vitro biocompatibility. the material cleared urea and creatinine without passing albumin, even at high flow rates. the clearance of urea and creatinine by cellulose-heparinase was equal or slightly reduced in comparison to the cellulose device. the cellulose-heparinase device tolerance to flow rates was also unchanged. in addition, scanning electron microscopy of the lumen established the uniformity of the material. the analysis of clearance rates and the scanning electron micrographs show there to be no damage to the cellulose membrane after tresyl chloride activation and heparinase immobilization. the investigation of biocompatibilty in an in vitro test system with whole human blood indicated that there were no significant changes in the biocompatibility of cellulose with bound heparinase. there was no change in the level of red blood cells, white blood cells, or platelets over the course of in vitro whole blood perfusion through cellulose or cellulose-heparinase hollow fiber devices. low levels of plasma hemoglobin and complement activation were observed with cellulose and cellulose-heparinase devices. (edited author abstract) 12 refs