Hsp70 is a highly conserved, ubiquitous molecule and its properties as a molecular chaperone are well-described. Additionally, it has been shown to carry out important functions in the mammalian immune system. This study addressed several open questions concerning the interaction of Hsp70 with the surface of antigen presenting cells and the mechanism of Hsp70-mediated cross-presentation. Hsp70 was shown to interact with the surface of antigen presenting cells but not with non-immune cells. This binding was dependent on the nucleotide state of the chaperone. Only the peptide-loaded, ADP-conformation of the molecule showed the described cell-surface interaction, while the empty, ATP-loaded state did not. Previously published receptors for Hsp70 interaction with antigen presenting cells were critically evaluated and shown not to play a considerable role in this interaction. The specific binding of Hsp70 was shown to be conferred by at least two distict interactions, namely by the N-terminal ATPase domain in one case and the C-terminal substrate binding domain in the other case. The interaction of Hsp70 with the APCs was shown to lead to crosspresentation of chaperoned peptide on the cells’ MHC class I molecules. Isolated ATPase and substrate binding domain of Hsp70 were analyzed for this function and the cross-presentation capabilities were mapped to the substrate binding domain. Additionally, an attempt was made to understand the intracellular pathway of the Hsp70/peptide complex, and an assay was developed which allows analysis of the contribution of individual compartments employing dominant negative mutants of small GTPases.