Increasing numbers of interventional radiologic procedures, often with large arterial catheters, have led to increasing total numbers of complications. Pseudoaneurysm is not an infrequent complication. It is often difficult to differentiate pseudoaneurysm clinically from hematoma. In the past, we have used gray scale duplex scanning to aid in this differentiation. We have recently found color Doppler scanning to allow quicker, easier, and more accurate diagnosis. Color Doppler imaging also can often demonstrate the track between the artery and the aneurysm.