Hemodynamic basis of stasis ulceration--a hypothesis. Approximately 25% of patients with stasis ulceration have normal or below normal ambulatory venous pressures. A reflux index was calculated by multiplying postexercise pressures by Valsalva-induced foot venous pressure elevation. In patients with stasis ulceration, reflux index was found to have an excellent negative predictive value with a clear discriminant line between normal limbs and those with ulcers. Increasing incidence of stasis ulceration was demonstrated with increasing reflux index value. Even when ambulatory venous pressure was within the normal range, the index was found to be abnormal in ulcerated limbs because Valsalva-induced foot venous pressure was elevated in these limbs. Conversely, some patients with stasis ulceration and normal Valsalva foot venous pressure elevation were found to have abnormal ambulatory venous pressure values, yielding an elevated reflux index. Preliminary analysis indicates that reflux index may be a better predictor of surgical outcome after valve reconstruction procedures than either ambulatory venous pressure or Valsalva-induced foot venous pressure elevation. The concept of reflux index is a hypothesis that attempts to explain inconsistencies observed in implicating ambulatory venous hypertension as the sole determinant of venous reflux. 