White blood cells have recently been implicated in the development of venous ulceration. Fifty subjects (14 normal controls, 21 with superficial venous insufficiency (SVI), and 15 with deep venous insufficiency (DVI] have been studied in the supine and dependent positions in a constant environment using video capillary microscopy, laser Doppler flowmetry and transcutaneous oxygen measurements to the gaiter skin. All three groups had an increase in visible capillary loops and a reduction in blood flux in the gaiter region when the leg was placed in the dependent position. There was a decrease in the leg/chest transcutaneous oxygen ratio in all three groups on dependency. These results suggest that the 'oedema protection reflex' (as measured by the laser Doppler probe) is present not only in normal and SVI limbs but also in DVI limbs. The increase in visible capillary loops suggests that intraluminal capillary occlusion is not occurring within the period of this study. The exact microvascular defecit of venous ulceration remains to be explained.