The aim of this study was to label exorphin C with Tc-99m and to examine its usefulness as opioid receptor binding radiopharmaceutical in Albino Wistar rats. Exorphin C, which is a peptide with 5 aminoacids, was labeled with Tc-99m using glucoheptonate (GH) as a bifunctional chelating agent. Labeling efficiency was higher than 98%. The compound was stable for at least 5 hours at room temperature. Mammary tumor bearing Albino Wistar rats were imaged using gamma-camera. Biodistribution studies were also performed. Results demonstrated that Tc-99m-glucoheptonate-exorphin C(Tc-99m-GE) analogs may be useful as a new class of receptor-binding peptides for the diagnosis and therapy of some cancer diseases related with opioid receptor-expressing tissues.