Our model that includes non-genetic factors such as age, diabetes and hypertension as well as genetic variants in VKORC1 (rs9923231), CYP2C9 (rs2860905 and 1856908), CES2 (rs4783745), and ABCB1 (rs10276036), explained 60% of the variability in warfarin dose requirements among Puerto Ricans. The gene discussed is CYP2C9; the disease is diabetes mellitus.