['Factor V Leiden has been reported in 2%-30% of patients with portal vein thrombosis. This wide variation makes it difficult to assess the importance of factor V Leiden as a predisposing factor.', 'Factor V Leiden was determined by restriction fragment length polymorphism in 112 patients with portal vein thrombosis, 104 with deep vein thrombosis and 98 control subjects.', 'Only 3/112 (3%) patients with portal vein thrombosis had factor V Leiden, compared to 1/98 (1%) controls and 16/104 (15%) with deep vein thrombosis; of these, 3, 1 and 15, respectively, were heterozygous for this mutation.'] Is factor V Leiden commonly associated with idiopathic portal vein thrombosis in southern India?