APN is an important zinc dependent metallo-exopeptidase; it has been considered as a suitable target for anti-cancer drug design. In this review we focus on the most effective and the most promising inhibitors of aminopeptidase N. Their binding modes to the enzyme, the attempt to explain the origin of the inhibitory activity, as well as the structure-activity relationship for some of these compounds are discussed. Besides, the structural and electronic requirements of the enzyme active site and the binding pockets, together with the specificity towards the ligands are presented.