The purpose of this study was to compare pulse oximetry with ankle and toe pressure measurements in a group of 25 patients with lower limb ischaemia. Measurements were performed on 49 limbs. Pulse oximetry recordings from the second toe were obtainable in only 28 (57%) cases. With lower ankle or toe pressure and more severe symptoms, oximetry was less likely to be possible. In all cases of successful recordings, the oxygen saturation at second toe level was identical with the finger saturation. These data indicate that pulse oximetry has no value in the assessment of peripheral arterial occlusive disease.