BACKGROUND Patients with lipodermatosclerosis (LDS) due to chronic venous disease (CVD) of the lower limb show proliferation and convolution of their skin capillaries. There has been no previous attempt to quantify the severity of venous disease according to the extent of morphological change. OBJECTIVE To quantify capillary damage in patients with CVD using capillary microscopy. METHODS 132 patients attending the vascular clinic for management of CVD were examined clinically and by duplex ultrasonography; they were assigned to the appropriate CEAP clinical stage by a surgeon. Ten control subjects with no arterial or venous disease of the lower limb were also studied. Digital images of the skin microcirculation were obtained using a CAM1 microscope. In patients with skin changes the most severe regions of LDS were studied. In all other subjects the region 5 cm proximal to the medial malleolus was investigated. The total number of visible capillaries and capillary convolutions was counted in a 2.4 mm2 region. RESULTS The more advanced stages are associated with the reduced numbers of capillaries. The number of convolutions is greatly increased in the more severe stages, C4b and C5. These have been graded in four classes. The capillary counts (per square mm) and convolutions per capillary in C0, C2 and C5 patients are 8(6-11), 1(1-1); 6(4-9), 1(1-2); 3(3-4), 7(6-8), respectively. CONCLUSIONS Amongst patients with venous disease, capillary convolution is strongly associated with the more severe stages (LDS and healed ulceration), which can reliably be reproduced by capillary microscope.