Preoperative venous duplex scanning has revealed unexpected deep venous incompetence in patients with apparently only varicose veins. Acting on the hypothesis that the deep vein reflux was secondary to deep vein dilation caused by reflux volume, the following was done. Between July 1990 and April 1993, 29 limbs in 21 patients (16 females) were examined by color-flow duplex imaging to determine valve closure by the method of van Bemmelen. Instrumentation included high-resolution ATL-9 venous interrogation using a pneumatic cuff deflation stimulus of reflux in the standing, nonweight-bearing limb. All limbs showed greater saphenous vein reflux. Twenty-nine showed superficial femoral vein reflux and of these three showed popliteal vein reflux. Duplex testing was performed by a certified vascular technologist whose interpretation was blinded as to the results of clinical examination and grading of the severity of venous insufficiency. Surgery was performed on an outpatient basis under general anesthesia using groin-to-knee removal of the greater saphenous vein by the vein inversion technique of Van Der Strict. Stab avulsion of varicose tributary veins was accomplished during the same period of anesthesia. In 27 of 29 limbs with preoperative femoral reflux, that reflux was abolished by greater saphenous stripping. In patients with popliteal reflux both femoral and popliteal reflux was abolished. Improvement of deep venous hemodynamics by ablation of superficial reflux supports the reflux circuit theory of venous overload. Furthermore, preoperative evaluation of venous hemodynamics by duplex scanning appears to provide useful pre- and postoperative information regarding venous insufficiency in individual patients.