A study carried out to determine whether coumarin-associated liver dysfunction is genetically determined by polymorphism in CYP2A6 and impairment of the 7-hydroxylation of coumarin [90] demonstrated that here was no significant difference in the incidence of liver dysfunction between heterozygotes with CYP2A6*2, CYP2A6*3 and wild-type homozygotes. The gene discussed is CYP2A6; the disease is Decreased liver function.