The Aspartic proteases (EC 3.4.23) are a group of proteolytic enzymes that share the same catalytic apparatus. Members of the aspartic protease family can be found in different organisms, ranging from humans to plants and retroviruses. The best known sources of aspartic proteases are the stomach of mammals, yeast and fungi, with porcine pepsin as the proto type. The aim of this review is to summarize some of the characteristics of the aspartic protease family.