The increase in venous pressure during leg dependency causes a vasoconstriction of the distal vascular bed in healthy subjects, which is due to the so-called veno-arteriolar reflex. The aim of the present study was to investigate if this reflex is disturbed in patients with severe peripheral arterial occlusive disease (PAOD), with and without diabetes. The total skin microcirculation during rest and postocclusive reactive hyperemia (PRH) after a three minute arterial occlusion at the ankle was studied by laser Doppler (LD) fluxmetry. The LD probe was attached to the dorsal region of the foot in 10 legs of healthy control subjects, patients with PAOD, and patients with PAOD and diabetes respectively. No vasoconstriction was seen in the PAOD group when the leg was moved from the supine to the dependent position. The PRH response was also significantly (p less than 0.05-0.01) impaired compared to the controls in both positions. The diabetic PAOD patients had an almost normal reactivity in spite of an equally reduced arterial circulation as the non-diabetic patients. The results show that patients with PAOD have a significantly disturbed reactivity of the skin microcirculation in the ischemic foot, while the reactivity in diabetic PAOD patients is almost normal.