Protease nexin-2/amyloid β-protein precursor (PN-2/AβPP) and its Kunitz protease inhibitory (KPI) domain were characterized as inhibitors of factor VIIa (FVIIa) and factor VIIa–tissue factor complex (FVIIa–TF). PN-2/AβPP and KPI domain inhibited FVIIa with an apparent K i of 1.1±0.2× 10 −7 M and 1.5±0.1×10 −7 M, respectively. When soluble tissue factor (TF 1–219) was present, there was increased FVIIa inhibition by PN-2/AβPP or KPI domain ( K i=7.8±0.3×10 −8 M and 6.8±0.6×10 −8 M, respectively). When relipidated tissue factor (TF 1–243) was present, the K i of FVIIa inhibition by PN-2/AβPP increased 4.7-fold further K i =1.65× 10 −8 M . PN-2/AβPP complexed with FVIIa, as shown on gel filtration and solid phase binding assay. The apparent second-order rate constant of inhibition of FVIIa by PN-2/AβPP in the absence of TF 1–219 k″=7.5±4.0×10 4 M −1 min −1 was less than that of the FVIIa–TF 1–219 complex k″=1.6± 0.2×10 5 M −1 min −1 . Antithrombin in the absence of TF 1–219 also had a lower apparent second-order rate constant of inhibition k″=1.8±0.3×10 3 M −1 min −1 than in its presence k″=1.6±0.3×10 5 M −1 min −1 . In a mixture that included FVIIa, relipidated TF 1–243 and factor X, PN-2/AβPP or KPI domain had an IC 50 at 65 and 250 nM, respectively; antithrombin and heparin (1 U/mL) had an IC 50 of 12.8 nM. These data indicate that tissue factor promoted the inhibition of FVIIa by PN-2/AβPP or KPI domain, but antithrombin was a better inhibitor of soluble FVIIa–TF in extrinsic tenase.