Abstract: The present invention provides novel opioid peptides which are selective for the kappa opiate receptor. In one embodiment, the kappa-selective opioid peptides have the general structure Ac-A1-B2-C3-Arg-Tyr-Arg-Tyr-Arg-Arg-Arg-NH.sub.2, (SEQ ID NO. 28), wherein A1 is Tyr or Arg, B2 is Arg or Phe, and C3 is Thr, Phe, or Met. In yet other embodiments, the kappa-selective opioid peptides have the general structure (D)Phe-D4-E5-F6 (SEQ ID NO. 29) or (D)Nle-D4-E5-F6 (SEQ ID NO. 30), where in both of these formulae D4 is (D)NapAla or (D)Phe, E5 is (D)Nle, Trp, or (D)Ile, and F6 is (D)Arg or (D)ChAla.