Although biliary symptoms appear to be uncommon in patients with portal cavernoma, almost all of them have endoscopic retrograde cholangiographic abnormalities. The mechanisms underlying the biliary changes are explained poorly. This study in patients with portal cavernoma had 3 aims: (1) to assess the manifestations related to biliary involvement; (2) to evaluate with magnetic resonance (MR) imaging the aspect and frequency of cholangiographic changes; and (3) to clarify the mechanisms underlying biliary involvement. From December 1999 to July 2001, 25 consecutive adults with portal cavernoma without cancer or cirrhosis were studied with MR cholangiography coupled with MR portography. Seven patients presented with clinical manifestations of biliary disease. MR cholangiography findings were stenosis in 21 patients, with upstream dilatation in 16 and displacement in 13. MR cholangiography coupled with MR portography showed in all cases that the biliary abnormalities were secondary to a mass effect directly related to pressure by the cavernoma. In conclusion, in patients with portal cavernoma, clinical manifestations of biliary disease are most frequent; the cholangiographic abnormalities are very common and usually are caused by a mass effect by pressure from the veins composing the cavernoma. MR cholangiography coupled with MR portography is an effective noninvasive examination for simultaneous visualization of bile ducts and their relationship to the cavernoma.