Two mutations within genes in the blood coagulation pathway that have been implicated as significant factors for thrombotic risk. These two defects, factor V Leiden and prothrombin 20210A, are responsible for over 60% of all cases of inherited thrombophilia. In addition to being significant risk factors for hypercoagulation, the mutations are frequently found in, but are not limited to, people of European descent. Carriers of the Leiden R506Q mutation have an 8 fold increased risk for venous thrombosis and homozygotes have a 91 fold increased risk. Specific acquired or environmental factors may dramatically increase this baseline risk. Approximately 5% percent of the Caucasian population carries the Factor V Leiden mutation. Three percent of the Caucasian population carries the prothrombin mutation. The molecular diagnosis of these mutations is done with the polymerase chain reaction and restriction endonuclease digestion or allele specific oligonucleotide amplification.