Abstract/Text: Air-plethysmography has been used to measure, in ml and in ml 100 ml-1 of tissue, the blood volume that filled the leg veins on changing posture from the recumbent position to standing. The venous filling index (VFI) (average filling range) was measured in ml s-1 and in ml 100 ml-1 min-1. We studied 24 normal legs (N), 21 with primary varicose veins without chronic swelling, skin changes (liposclerosis, eczema, pigmentation) or ulceration (PVV) and 59 with chronic swelling and/or skin changes and/or ulceration; of these 59 legs, 31 had primary varicose veins (PVV/S) and 28 had popliteal reflux (PR). The classification was done according to clinical examination, Duplex scanning, ambulatory venous pressure measurements and venography. There was an increased incidence of sequelae with increasing values of VFI. The incidence of these sequelae was irrespective of whether reflux was in the deep or in the superficial veins. VFI is a practical non-invasive measurement of reflux. It should be used to study the effect of therapy and particularly to evaluate new reconstructive procedures designed to abolish reflux in the deep veins.