Eighty-five limbs in 73 patients with a healed venous ulcer were assessed by ascending and descending phlebography, foot volume plethysmography and transcutaneous oxygen measurements. Forty-four limbs had post-thrombotic changes on ascending phlebography. In 24 (28 per cent) these extended into the femoral vein, while in 20 (24 per cent) only the calf veins were involved. In the 41 limbs (48 per cent) with normal deep veins on ascending phlebography, 11 had evidence of localized incompetence of the calf communicating veins, 14 had either long saphenous incompetence, deep vein reflux to the level of the knee or below, or both of these abnormalities, and 16 limbs had no phlebographic abnormalities. However all limbs had a decreased half volume refilling time on foot volume plethysmography. Limbs with post-thrombotic changes extending into the femoral vein were associated with a significantly longer history of ulceration and more ulcer recurrences than limbs with calf vein damage (P less than 0.05 for each) and limbs with normal deep veins (P less than 0.01 for each). However, these limbs did not have lower transcutaneous oxygen ratios or longer times to achieve ulcer healing. Ascending phlebography identified a group of limbs with extensive post-thrombotic changes in which there was a higher incidence of ulcer breakdown, but this was not associated with a delay in ulcer healing.