Lipoperoxide has been detected in the thoracic duct lymph of the dog. This finding suggests that lipoperoxides are normally transported in lymph and with impaired lymph drainage may be deposited in the skin and contribute to the soft tissue changes characteristic of chronic lymphedema. Accordingly, after obtaining skin specimens taken from 8 patients (7 with obstructive lymphedema) with lower extremity lymph stasis we determined dermal malondialdehyde (MDA) content (after conversion to fluorescent thiobarbituric acid or TBA), a marker of lipoperoxide. In all 7 patients with obstructive lymphedema, the MDA levels were increased compared to control dermis (p < 0.05). We suggest that inability to clear lipoperoxides from the dermis with lymphatic insufficiency may contribute to the pathogenesis and structural skin derangements of chronic lymphedema.