The rescent discovery of carrier peptides offers new opportunities to translocate several bioactive molecules into the cytoplasm. Previous studies have shown that human calcitonin (hCT) and selected C-terminal sequences translocate in nasal epithelium. Moreover, the hCT(9-32) fragment was found to internalize efficiently a number of substances like fluorophores, nucleic acids or the enhanced green fluorescent protein (EGFP). In order to understand the uptake mechanism interactions of hCT(9-32) with membrane models of different lipid compositions have been investigated. From these studies it was possible to shed light on the conformational state of the peptide in the presence of membrane-like conditions. Further insight into the translocation mechanism was provided by fluorescence microscopy of truncated sequences of hCT that were shown to penetrate the plasma membrane and to distribute in a sectoral, punctuated pattern supporting an endocytotic internalization pathway as previously suggested.