Maurocalcine (MCa) is the first natural cell penetrating peptide to be discovered in animal venom. In addition to the fact that it represents a potent vector for the cell penetration of structurally diverse therapeutic compounds, MCa also displays several distinguishing features that make it a potential peptide of choice for clinical and biotechnological applications. The aim of the present study was to gain new information about the properties of MCa in vivo in order to delineate the future potential applications of this vector. For this purpose, two analogues of this peptide with (Tyr-MCa) and without (Lin-Tyr-MCa) disulfide bridges were synthesized, radiolabeled with I-125, and their in vitro stabilities were first evaluated in mouse blood. The results indicated that I-125-Tyr-MCa was stable in vitro and that the disulfide bridges conferred a competitive advantage for the stability of peptide. Following in vivo injection in mice, I-125-Tyr-MCa targeted peripheral organs with interesting quantitative differences and the main route of peptide elimination was renal.