AbstractSeventy-four adults with documented deep-vein thrombosis of the pelvis and/or lower extremities had baseline and follow-up radionuclide venography (RNV), giving a total of 171 studies. Fifty-nine of the patients had unilateral venous thrombosis, of which 36 (61.0%) involved the left side and 23 (39.0%) the right. The higher incidence in the left side was attributed to the longer and more horizontal course of the left common iliac vein, as well as to compression by the right iliac artery and inguinal ligament. In 13 patients bilateral involvement was noted. “Normalisation” of the venous circulatory pattern was characterised by recanalisation and partial or significant disappearance of abnormal collaterals. This occurred in 43/74 patients. In 24 cases, no change was recorded during the interval, while seven patients deteriorated.