Introduction <p>Chemotherapeutic drugs invariably induce significant cytotoxic side effects in cancer patients and often lead to the expansion of drug-resistant clones. Considerable efforts have been invested over recent years in developing drug delivery systems aimed at limiting drug activity to the target cell. Achieving this goal depends on several factors, not the least of which is the ability to select appropriate drug carriers. While antibodies are a popular choice as a drug carrier, there are several important challenges in their use. Peptides have emerged as a viable alternative to antibodies. Many technologies have been developed that allow the screening of large (&gt; 10^10–12) libraries of peptide ligands.</p> About this review <p>This review focuses on these technologies. First, we discuss the more advanced of these techniques, such as aptamers, ribosome display, and microorganism-based technologies, in particular phage display. We then compare the clinical effectiveness of these techniques, judged by their ability to generate targeting peptides used in targeted drug delivery systems that have shown clinical efficacy. Our review of the literature indicates that phage peptide display is a superior platform for the discovery of peptides for the construction of peptide-drug-conjugates that could significantly improve the efficacy of cancer chemotherapy.</p>