A study of the arterial patterns of the upper limbs in Lorisiformes (Prosimiae), especially those of the rete mirabile and their correlating arteries, was carried out by three-dimensional arteriographic analysis.The rete displayed at least two types of plexiform distribution: (1) a vascular bundle in Lorisidae, which consists of a division of the main artery into a principal trunk surrounded upwards by about 50 small arteries, and (2) a simple network pattern in Galagidae, which, at most, is composed of simple vascular networks of the nature of a few widely scattered anastomoses. The arterial patterns of the upper limb in Lorisiformes are basically the same, but the position of divergence and the number and size of the vessels in the rete differ. The arterial patterns of the upper limbs in Lorisiformes closely resemble the development of the vessels in the 21- to 23-mm stages of human embryonic growth. In this study, we observed some similarity in the patterns between the rete mirabile and the superficial brachial artery in man.