Possession of a variant Cytochrome P450 2C9 (CYP2C9) genotype has been associated with a higher risk of hemorrhagic complications among warfarin users. [1; 2] Although the influence of the common variant alleles (CYP2C9*2, CYP2C9*3) on warfarin response is well documented that of other rare defective alleles, CYP2C9*5, the null allele CYP2C9*6 and CYP2C9*11 found in African-Americans [3; 4] has not. The presence of these alleles may represent the higher genomic sequence diversity in populations of African descent. Herein we describe discovery of a new putative deleterious CYP2C9 polymorphism identified in an African American participant from an ongoing prospective study during routine testing.[5] Analysis of the patient’s genotype identified a new CYP2C9 polymorphism G1078A coding for a D360N in the coding region of exon 7 one codon downstream from the I359L coding change seen in CYP2C9*3.