In recent years, we have witnessed a rapid expansion of our knowledge regarding the role of the endothelium in the control of vascular tone (and organ perfusion) in health and disease. Physiology, pharmacology, and molecular biology have uncovered a wealth of information on structure and function of this heretofore largely neglected "organ". Clinical medicine is now called upon to define the clinical significance of these observa tions that imply the mechanisms of blood coagulation, e.g., the interaction of throm bocytes with the endothelium, vasomotor control, and specifically, the regulation of smooth muscle tone with consequences for vascular resistance and conductance and organ blood flow. Finally, metabolism of lipids with the everlasting problem of athero sclerosis is an important aspect. In a second step, implications regarding the improvement of current therapeutic con cepts, as well as the development of new modalities of pharmacotherapy will have to be discussed. The topic addressed by the 1990 Gargellen Conference: Endothelial Mechanisms of Vasomotor Control, clearly is of interest for both basic scientists and clinicians. It has been the aim of the organizers, the Society for Cooperation in Medical Science (SCMS) with this and the previous symposia to foster and support both basic science and clinical research. Research in medicine today shows two major directions of development: on the one hand, increasing involvement of the basic sciences and their methodology. On the other hand, statistical validation of concepts and therapeutic strategies in large scale population-and multicenter-studies.

A vast literature has been concerned with arteriosclerosis and yet, many aspects of pathogenesis and of the mechanism of development of the arteriosclerotic vascular lesion remain only poorly understood. In recent years, our knowledge of the earliest stages of arteriosclerosis have greatly improved. By now, we have learned to relate morphologic changes to disturbances in function. It has been of particular impor tance that components of the arterial wall could be analyzed in regard to dysfunction, for example, in the endothelium or the vascular smooth muscle. The interaction of the different morphological components of the vascular wall could thus be much bet ter understood. Likewise, the interaction between the arterial wall and the flowing blood could be much better described, including the intimate relationship between platelets and the endothelium, the coagulation system and the endothelium, the granulocytes and the endothelial cell layer, as well as processes of migration of blood cells into the subendothelial space. The recognition of functional and morphological disturbance has attained clinical significance not only because the arteriosclerotic diseases have quantitatively reached the dimensions of an epidemic, that is, of a magnitude never been witnessed. It is also because of the development of new drugs that interfere with the atherogenic process and thereby prevent the development of the disease or halt its progression. It is also becoming increasingly possible to inhibit the occurrence of complications in existing arteriosclerotic lesions in manifest disease, i. e.