Abstract: The present invention is directed to a group of linear and cyclic peptides having the structures: ##STR1## These peptides, when systemically administered to animals will bring about a sexual response and are thus useful for the diagnosis and treatment of psychogenic sexual dysfunction in the male.

Abstract: Several known members of the corticotropin releasing factor (CRF) family have been synthesized and tested, including human and rat CRF which have the formula: H-Ser-Glu-Glu-Pro-Pro-Ile-Ser-Leu-Asp-Leu-Thr-Phe-His- Leu-Leu-Arg-Glu-Val-Leu-Glu-Met-Ala-Arg-Ala-Glu-Gln- Leu-Ala-Gln-Gln-Ala-His-Ser-Asn-Arg-Lys-Leu-Met-Glu- Ile-Ile-NH.sub.2. Peptides are herein disclosed that are potent competitive antagonists of CRF in mammals. One which has been found to be particularly potent is: H-D-Phe-His-Leu-Leu-Arg-Glu-Val-Leu-Glu-Nle-Ala- Arg-Ala-Glu-Gln-Leu-Ala-Gln-Gln-Ala-His-Ser-Asn- Arg-Lys-Leu-Nle-Glu-Ile-Ile-NH.sub.2. One that has shown particularly prolonged duration of potency is: H-D-Phe-His-Leu-Leu-Arg-Glu-Val-Leu-Glu-Nle-Ala- Arg-Ala-Glu-Gln-Leu-Ala-Gln-Gln-Ala-His-Ser-Asn- Arg-Lys-CML-Nle-Glu-Ile-Ile-NH.sub.2.