14 patients with orthotopic liver transplantation were prospectively studied with MR imaging. MR imaging demonstrated a perivascular collar surrounding central portal venous branches in 14 patients. The perivascular collar had low signal intensity on T1-weighted and high signal intensity on T2-weighted images. In 10 of the 14 patients, a perivascular collar was also observed around peripheral portal venous branches. The perivascular collar is probably caused by intraoperative interruption of hepatic lymph vessels and resultant impaired lymph drainage. It is a normal postoperative phenomenon in hepatic transplants. MR imaging is particularly useful in the distinction of postoperative hematoma from other intra- and extrahepatic fluid collections and may provide a noninvasive assessment of liver transplant rejection.