A prospective study was performed to evaluate the usefulness of CT pelvic venography (CTV) in the detection of pelvic vein thrombosis in patients referred for CT pulmonary angiography (CTPA) for suspected pulmonary embolism. Fifty consecutive patients referred for CTPA had CTV performed at the time of CTPA. All patients had duplex ultrasound (DUS) of the lower limb veins for evaluation of deep venous thrombosis (DVT) within 24 h of the CT study. Twelve (24%) of the 50 patients had pulmonary embolism diagnosed on CTPA. Associated DVT was detected in six of these patients; two cases were detected by CTV alone, while one case was detected by both CTV and DUS. The remaining three cases had DVT diagnosed by DUS alone. In the 38 patients with a negative CTPA, three patients had venous thrombus diagnosed by CTV. Of these three patients, two had a negative DUS study. CTV therefore led to a definitive imaging diagnosis of thrombo-embolic disease in two (4%) more patients. CTV adds little time and cost to the CTPA examination and leads to a moderate increase in definite imaging diagnosis of thrombo-embolic disease.