Lower leg subcutaneous blood flow during walking and passive dependency in chronic venous insufficiency. The blood flow in the subcutaneous adipose tissue of the lower leg of eight normal subjects and 19 patients with chronic venous insufficiency was measured. The 133Xe-washout technique was used with portable CdT1(C1) detectors and a data storage unit. Only those patients with ulcers and a systolic blood pressure at the toe of greater than or equal to 60 mm were investigated. In the controls the relative blood flow during sitting was 0.61 (range 0.35-0.80). In the patients it was 0.46 (range 0.22-0.87). This difference was not significant. During walking the blood flow increased in controls as well as in the patients compared to the value determined in the sitting position (P = 0.0078 and P = 0.0028, respectively, Wilcoxon matched-pairs test). The relative blood-flow rate during walking was 0.96 (range 0.60-1.58) in the controls, and 1.04 (range 0.49-1.46) in the patients. The difference between the normal subjects and the patients was not significant (P = 0.79). We conclude from our studies that patients with venous insufficiency are able to increase their blood flow during walking to the same extent as normal controls. 