1. Twenty-four hour continuous recording of xenon (133Xe) wash-out from the forefoot was performed on patients with normal circulations (n = 10) and on patients with different degrees of arterial insufficiency (n = 36).
2. During day hours the calculated subcutaneous blood flow in the forefoot was on average the same in patients with normal circulations and in patients with different degrees of arterial insufficiency (mean: 2.0 ± 0.8 ml min−1 100 g−1).
3. During sleep the blood flow nearly doubled in patients with normal circulations; no systematic change was seen in patients with intermittent claudication. In patients with severe ischaemia, i.e. having rest pain, the blood flow decreased by approximately 50%.
4. The changes in local blood flow may be due to changes in local sympathetic tone and to changes in local perfusion pressure.