Abstract: Disclosed are compounds of the formula: X Y Z A P Q T which are highly potent, selective factor IIa inhibitors, X, when present, may be connected to T, may be H, CH.sub.3, an acyl group, or a general protective group. Y is D-DPA, D-Phe, D-Val, D-Ile, D-Nle, a phenylsulfonyl, Dansyle, or 8-(1,2,3,4-tetrahydroquinolinosulfonyl) compound. Z, when present, is Gly, L/D-Pro, L/D-Ala, L/D-Leu, aminoisobutyric acid, a substituted or unsubstituted L/D-Pro ring homologue, or L/D-Val. A may be (I) wherein M is --CO--CF.sub.2 --(CO).sub.s --, --(CO).sub.d --NH--, --(CO).sub.d --(CH.sub.2).sub.p --, or --CH(OH)--(CH.sub.2).sub.p --, d is 0-2, p and q are 0-5, and s is 0 or 1, or A is a proline-like group. P and Q (if Q is present) are substituted or unsubstituted amino acids selected from the group consisting of L/D-Phe, L/D-Cha, L/D-Nal(1), L/D-Nal(2), L/D-phenylglycinyl, L/D-Leu, L/D-Ile, L/D-Nle, L/D-Arg, L/D-Lys, or L/D-His. T may be connected to X, or may be --OH, --OR.sup.4, --NH.sub.2, --NHR.sup.4, or --NR.sup.4 R.