Immunosuppressive agents are commonly used to treat a variety of clinical disorders characterized by alteration in the immune system. These include collagen vascular diseases, inflammatory bowel diseases, dermatological conditions, graft-versus-host disease (GVHD) following haematopoietic stem-cell transplantation, and graft rejection following solid-organ transplantation. Over the last few years, drugs that specifically target lymphocytes have been developed and are now widely used against lymphoid haematologic malignancies. Some immunosuppressive agents have also been found to have antiproliferative effects and are now being studied in patients with solid tumours.