Aim: We conducted a genome-wide association study using the Illumina Exome Array to identify coding SNPs that may explain additional warfarin dose variability. Patients & methods: Analysis was performed after adjustment for clinical variables and genetic factors known to influence warfarin dose among 1680 warfarin users (838 European-Americans and 842 African-Americans). Replication was performed in an independent sample. Results: We confirmed the influence of known genetic variants on warfarin dose variability. Our study is the first to show the association between rs12772169 and warfarin dose in African-Americans. In addition, genes COX15 and FGF5 showed significant association in European-Americans. Conclusion: We identified some novel genes/SNPs that underpin warfarin dose response. Further replication is needed to confirm our findings.