Multiple myeloma, typically characterized by the accumulation of clonal plasma cells in multiple sites of the bone marrow, is the second most common hematologic malignancy with an incidence of 15,000 patients per year in the United States and a prevalence of approximately 50,000. Although the majority of patients respond to initial treatment with chemotherapy and radiation, most eventually relapse due to the proliferation of resistant tumor cells. Despite the advent of high dose chemotherapy with stem cell transplantation, multiple myeloma remains incurable, with approximately 12,000 deaths per annum recorded in the US from the disease. Over the last 10 years there has been a dramatic increase in our understanding of the biology of multiple myeloma which has provided insights into mechanisms of cytotoxic resistance both as inherent characteristics of the myeloma cell and the protective interaction between the tumor and its bone marrow microenvironment. Moreover, advances in our understanding of multiple myeloma pathogenesis have helped further define the intricacies of this complex disease. Through this greater understanding, a large array of new therapies have been engendered and a significant impact is being made on patient outcome as a result. This book provides a concise overview of the state of the art in multiple myeloma and should be of primary interest to clinicians as well as scientists and related caregivers alike in this rapidly changing field.