Prostaglandins are biologically extremely active substances and an important role has been attributed to them in particular with respect to pathophysiology of the cardiovascular system. In contrast to the extremely potent biological effects in vitro the therapeutic results have been varied so far. On the basis of these reports it has been prematurely concluded that prostaglandins are not of clinical importance. The fact that primary defects, as well as defects associated with the presence of other diseases, occur in conjunction with a disturbance in haemostatic regulation is gaining increasing attention. In contrast to the findings with coagulation disturbances, defects in the prostaglandin system seem predominantly to affect the arterial system. With increasing specificity of detection methods and broadening of the methodological spectrum the number of defects detected in the prostaglandin system is increasing. The place of prostaglandins in the development of vascular diseases and their importance with respect to clinical treatment cannot be assessed definitely as yet in view of the insufficiency of information in all areas at present.