Rituximab (MabThera®, Rituxan®) is a chimaeric murine/human antibody targeted against the surface antigen CD20 that is expressed on normal and malignant human mature B cells, but not stem cells or plasma cells. It is potentially the proverbial magic bullet for diseases associated with B cell disorders as well as a probe for elucidating the role of B cells in health and disease. This book explores the full spectrum of activity of Rituximab in man.