FOR ALMOST a century medical observers have described the hemorrhagic response to pinching, bruising, and needling the skin. These crude tests were the predecessors of the pressure capillary resistance tests, which have been the subject of considerable investigation in the past half-century, with results that have been diverse and often contradictory. The purpose of this review is to collect and evaluate the literature concerning such tests and to discuss the anatomic, physiologic, and environmental factors which influence capillary resistance. The effects of disease are outside the scope of this study. The term "capillary resistance" is not as accurate as "cutaneous vascular resistance," but it has the sanction of usage and will be used here. The term "capillary permeability" should be reserved for reference to the passage through the vessel walls of plasma and solutes, not blood cells. The pressure tests were initiated by Hecht's description of his negative-pressure ("suction") method