The essential function of the lymphatic system is to return to the vascular system extravascular molecules and colloids too large to re-enter directly. Quantitative lymphoscintigraphy employs this principle and has proved useful in the differential diagnosis of chronic limb swelling, in the identification of subtle or incipient lymphoedema and in edema of compound origin where a lymphatic component would otherwise go unnoticed. In a study exploring the contribution of lymphatic insufficiency to poor wound healing in chronic venous leg ulceration 32 patients were compared to 22 normal control subjects using quantitative lymphoscintigraphy. In subjects less than 65 years lymphatic function was reduced in the ulcerated limbs compared to normal limbs (p<0.0001). In those aged more than 65 years lymphatic function was lower in ulcerated limbs but not significantly so, owing to a decline in lymph drainage with age in normal controls (r = 0.62, p = 0.0001). In patients with unilateral leg ulceration lymphatic function was reduced in the ulcerated limb compared with the contralateral leg (<65 years, p = 0.05; >65 years, p = 0.03). The finding of impaired lymph drainage with chronic venous insufficiency suggests that lymphatic pathology may be as important as venous pathology in the "chronic venous leg ulcer" and treatment should be aimed at improving lymphatic as well as venous function.