Reactive hyperemia following ischemia in cutaneous tissue of human fingers was studied in 6 normal persons and 9 patients suffering from generalized scleroderma. Ischemia lasting 6 or 12 min was induced by inflating a cuff placed around the proximal phalanx to 300 mm Hg. Blood flow was measured by the local atraumatic 133Xenon wash-out technique. The following parameters were calculated: (1) Maximum blood flow was calculated from the steepest part of the wash-out curve following release of the cuff. (2) Excess cumulative blood flow, i.e., the integrated blood flow from release of cuff until preischemic blood flow values were obtained, minus preischemic blood flow times duration of ischemia. (3) Repayment, i.e., excess cumulative blood flow in percent of preischemic blood flow times duration of ischemia. Maximum blood flow, excess cumulative blood flow and repayment was decreased in the patients compared to normals. This might be due to structural changes of the blood vessel walls and/or functional changes of the vascular smooth muscle cells in scleroderma.