We examined the levels of oxygen on the skin of the gaiter areas of limbs with venous disease using a Roche Transcutaneous pO2 Monitor to determine whether hypoxia contributes to the skin changes and ulceration associated with severe venous disease. We studied patients with superficial varicose veins and no skin changes (Group 1: n = 25), patients with skin changes and healed ulcers (Group 2: n = 15), and an age matched normal control group (controls: n = 25). TcpO2 measurements were taken 5 cm above the medial malleolus with the limb both horizontal and vertical using a Roche Transcutaneous pO2 Monitor. A standard heel-raising test using a Medisonics Photoplethysmograph indicated the degree of venous insufficiency present. Results show that Group 1 patients and controls have similar skin oxygen levels (Group 1: TcpO2 66.48 + 14.12 mmHg; controls: TcpO2 61.60 +/- 11.02 mmHg) whereas those with skin changes and ulceration have significantly lower oxygen levels (Group 2: TcpO2 46.57 +/- 9.70 mmHg, t = 4.29, P less than 0.001). Group 2 patients did not show a significant rise in TcpO2 levels in the standing position whereas Group 1 patients and controls did (t = 2.6, P less than 0.02). PPG post-exercise recovery times confirmed differences between the three groups. These findings show that significant skin hypoxia occurs on the gaiter area of limbs with severe venous disease and support the concept of an oxygen diffusion block.