Abstract  New techniques are now available for studying skin microcirculation non-invasively in humans. The clinically most useful ones are laser Doppler fluxmetry, vital capillaroscopy, dynamic capillaroscopy and fluorescence microscopy. Some of these techniques have now been used in clinical practise for studying the reactivity of the skin microcirculation in patients with hypertension, hypotension and ischemia. It was found that the reactivity to stress in patients with hypertension can be quite different in the skin microvascular bed as compared to the total circulation of the region. In patients with local hypotension due to an arterial obstruction the postocclusive reactive hyperemia response is significantly changed compared to normals. The vasomotion activity is also decreased in the low, pressure area. A marked decrease in the local blood pressure may lead to tissue ischemia. In these patients the risk of skin necrosis can be evaluated by microscopic classification of the structural changes of the capillaries in the area of ischemia. When the skin capillaries are void of erythrocytes the risk of necrosis is imminent.