The enzyme aminopeptidase N (APN, also known as CD13) is a Zn²⁺ dependent membrane‐bound ectopeptidase that degrades preferentially proteins and peptides with a N‐terminal neutral amino acid. Aminopeptidase N has been associated with the growth of different human cancers and suggested as a suitable target for anti‐cancerous therapy. Different approaches have been used to develop new drugs directed to this target, including enzyme inhibitors as well as APN‐targeted carrier constructs. This review discusses the prevalence and possible function of APN in malignant diseases, mainly solid tumors, as well as its “drugability” evaluated in preclinical in vivo models, and also provides a brief overview of current clinical trials focused on APN. (Cancer Sci 2011; 102: 501–508)