Muscular clearance as the maximum blood flow in the M. tibialis anterior was determined with 133Xe in 78 patients before and after percutaneous transluminal angioplasty (PTA) of the femoral artery. The increase in maximum blood flow after successful PTA was 33.1%, which is consistent with the results of other investigators. In contrast to the clinical findings (OAD state according to Fontaine) obtained before and after PTA, the muscle clearance worsened in 42.6% of the cases studied. In 85% of the patients, the angiographic findings (stenosing arteriosclerosis of the A. tibialis anterior) explained the cause of this observation; these findings should therefore be available before the muscle clearance is studied.