The investigation of inherited bleeding disorders with routine tests of hemostasis will yield clear diagnostic information in the majority of subjects with an unequivocal history of bleeding and especially in those where the phenotypic severity is severe and where an obvious family history of bleeding is present. Nevertheless, a significant minority of subjects with obvious bleeding symptoms will remain without a definite diagnosis after extensive hemostatic testing. With these facts in mind, the role of molecular testing for inherited disorders of hemostasis now includes the following: confirmation of a phenotypic diagnosis through targeted genetic analysis, the distinction of bleeding phenocopies by molecular analysis, and provision of genetic testing as the investigation of choice in situations such as prenatal diagnosis and detection of the carrier state for inherited bleeding traits. In addition, molecular testing can sometimes be used to provide supplementary knowledge that can be used to enhance clinical care. Finally, the utility of genome-wide approaches to identify novel genetic associations may provide new information to explain the cause of bleeding in the population of bleeders without established diagnoses.