This paper describes the successful preparation and evaluation of peptide YY3–36 [PYY(3–36)] dry-powder inhalation formulation. Previously, this peptide has shown efficacy in appetite suppression when dosed by injection. Systemic pharmacokinetics—a key endpoint in comparing different delivery methods and doses—were evaluated for PYY3–36 delivery by intraperitoneal and subcutaneous injection and inhalation and then used to select doses in an appetite-suppression pharmacodynamic study.