The activated protein C resistance (APCr) phenotype is found in around 40% of thrombophilic Mexican Mestizo individuals; since only very few display the factor V gene Leiden (Arg506Gln) mutation, it was considered of interest looking for other factor V gene mutations associated to thrombophilia: The HR2 haplotype, the factor V Cambridge (Arg306Thr), the factor V Hong Kong (Arg306Gly) and the FV Liverpool (Ile359Thr). In 39 individuals, the FV Leiden was found in 10%, the HR2 haplotype in 28%, the FV Hong Kong in 2%, whereas the FV Cambridge and FV Liverpool gene mutations were not found in any individual. In the subset of 10 patients with the APCr phenotype, the FV Leiden mutation was found only in 4 (40%) whereas the HR2 haplotype in 3 (30%); all the patients with the factor V Leiden mutation and 27% of those with the HR2 phenotype displayed the APCr phenotype. It is concluded that these polymorphisms of the factor V gene are not major contributors to the thrombophilia observed in Mexican Mestizos and that additional mutations in the FV gene should be looked for in those who display the APCr phenotype.