urokinase (uk) was immobilized to the lumen of dacron-reinforced fibrocollagenous tubes (uk-fct) using a glutaraldehyde entrapment process, in an effort to develop a fibrinolytic small diameter (i. e. , 4 mm i. d. ) vascular graft soluble and immobilized urokinase were evaluated for their ability to lyse synthetic clots made from purified physiologic substrates, $alpha$ //2 plasmin inhibitor ( $alpha$ //2pi) mediated whole canine blood (wcb) and $alpha$ //2pi-depleted wcb by measuring lysis time and fibrin degradation product (fdp) formation. lysis times were orders of magnitude lower and fdp formation rates were orders of magnitude higher with synthetic clots compared with either $alpha$ //2-mediated or $alpha$ //2-depleted wcb clots as a substrate, using both soluble and immobilized uk. however, both soluble and immobilized uk catalyzed fdp formation at an enhanced rate for $alpha$ //2pi-depleted wcb compared with the inhibitor-mediated substrate. (edited author abstract) 9 refs