Warfarin is one of the most widely used coumarin anticoagulants. However, its use is made difficult by the wide interindividual variation in dose required to achieve a therapeutic effect, the narrow therapeutic range, and the risk of serious bleeding. Warfarin dose requirement, which varies 20-fold, is influenced by factors such as intake of vitamin K, ethnicity, illness, age, gender, concurrent medication, body mass index and genetic factors. Warfarin acts through interference with the recycling of vitamin K in the liver, which leads to secretion of inactive vitamin K-dependent proteins and this is controlled by many genes coding for enzymes involved in this action such as CYP2C9, Calumenin and VKORC1. We have studied polymorphisms of these three genes in 50 warfarin treated patients using RFLP-PCR and PGX-thromo stripassay and correlated these polymorphisms with the age, sex, warfarin therapy duration and dose and we found that warfarin maintenance dose is lower in patients with mutant CYP2C9 gene and VKORC1 gene than those with wild types genes (p = 0.05 and 0.044 respectively); also the same conclusion was reached regarding Calumenin gene, however it was not statistically significant (p=0.135). Clinical and laboratory features didn’t differ significantly between those with wild type and mutant type genes. Our results suggest that patients treated with warfarin having any of these genes or combined ones in mutant status may require lower maintenance dose.