Described is an N-terminal hexapeptide fragment of maximakinin, QUB 698.8, which exhibits potent tissue selective actions on smooth muscle. It demonstrates a high degree of selectivity for arterial smooth muscle over small intestinal smooth muscle, causing potent relaxation of arterial smooth muscle, while causing less potent contraction of ileal smooth muscle. It may be used treatment of diseases of the cardiovascular system and in promotion of angiogenesis.