Activated, but not nonactivated platelets, adhere well to D-dimer, and the adhesion is inhibited by 7E3 and eptifibatide, but not by 10E5. EDTA enhances adhesion of nonactivated platelets to D-dimer. Washed platelets were either not activated or were activated with T6 (25 μM) and then added to wells precoated with fibrinogen or D-dimer. After 1 hour, the wells were washed, and residual platelet adhesion was assessed by measuring residual alkaline phosphatase activity, reported as optical density adhesion units (AU). In some experiments, EDTA (10 mM), 10E5 and 7E3 (both 50 μg/mL), or eptifibatide (100 μM) was incubated with the platelets for 20 minutes at room temperature before the platelets were added to the wells; n = 5 (5 different experiments with 3 replicates of each condition) for all conditions except for studies of 7E3 and eptifibatide, where n = 3 (3 different experiments with 3 replicates of each condition).