The majority of this textbook is devoted to basic aspects of hemostasis and thrombosis and specific hemostatic and thrombotic diseases. But more common in clinical practice are disorders in which hemostasis and thrombosis are complicating features of another pathologic process. In latter disorders, the homeostatic balance that maintains the fluidity of the blood, while at the same time leaving it poised to prevent hemorrhage after trauma, is perturbed by systemic processes to cause bleeding, thrombosis, or both. This section of the textbook considers the potential for hemorrhagic or thrombotic manifestations in select patient groups, from conception to old age. The goal of these chapters is to provide a conceptual framework for understanding pathogenesis. Details of treatment are provided in chapters devoted to individual therapeutic agents or to specific thrombotic and hemorrhagic events.