Thrombosis of the abdominal veins is a rare clinical condition which can be assimilated with the more frequent localization of deep venous thrombosis of the lower limbs. In the last few years great attention has been paid to possible risk factors for thrombosis of the abdominal veins. Two risk factors that have been identified are the presence of internal diseases and congenital and/or acquired abnormalities of haemostasis. The authors describe 3 clinical cases (splenic and portal thrombosis due to congenital thrombophilia, Budd-Chiari syndrome, portal cavernoma consequent to ovarian neoplasia) with different etiopathogenesis to show how this apparently rare condition is today more frequently encountered and easier to recognize. In the presence of thrombosis of major venous structures the search and the identification of intrinsic internal risk factors and of congenital and acquired thrombophilic disorders remains of great importance. Screening for thrombophilia includes blood C and S proteins, AT III, homocysteine, Leiden mutation of the factor V gene, G20210A mutation of the prothrombin gene, antiphospholipid antibodies. The presence of one or more of these risk factors allows the identification of the cases of portal thrombosis (EHPVO) responsible for about 10% of all the cases of portal hypertension, without cirrhosis or other hepatic lesions. The primary diagnostic procedure however remains color-Doppler ultrasonography which represents the most simple and the cheapest diagnostic investigation for the study of the portal and suprahepatic vein system, but it's strictly operator dependent.