The surface of a cell represents a collection of macromolecules, which provides the cell with a unique cellular landscape specific to the type and state of the cell. Ligands that discriminate between subtle differences in cell surface phenotypes have utility in a wide variety of research and clinical applications. In particular, cell binding ligands that can deliver biologically active cargo to a specific cell type or a diseased cell are highly sought. Towards the goal of isolating cell targeting ligands, our laboratory utilizes phage display panning protocols to identify peptides that mediate binding and uptake into cells. A remarkable feature of the peptides selected using this panning procedure is their cell-specificity. The high discriminating power of the selected phage allows us to selectively target different cell types, even those of similar types or classifications. The approach employs an unbiased screen in which there is no selective pressure towards binding a particular macromolecule. This has the important advantage that it requires no prior knowledge of the cellular receptor. We are currently focused on the isolation of cell-targeting reagents for different solid tumors.