Platelet size and count are associated with cardiac ischemia and ischemic stroke, two of the most common forms of acute cardiovascular disease. While platelet count (PC) is a common clinical measure, assessment of platelet size using mean platelet volume (MPV), the average size of platelets in a blood sample, and platelet distribution width (PDW), the variance of the platelet volume curve, are less frequently used. The overall objective of my research is to characterize these three quantitative platelet measures in a population of healthy individuals and evaluate the genetic and environmental determinants of these traits. Clinical and anthropometric predictors were examined in addition to a genome-wide association study (GWAS) conducted for each of these three quantitative platelet traits. 23 SNPs were associated at a suggestive level of significance (p<1x10-5) and some associated loci were near plausible candidate genes. MPV, PC, and PDW are heritable traits and improved understanding of their genetic and environmental underpinnings could provide novel insight into platelet biology.