Patients ages 18 to 72 who have MDS that requires transfusions and who do not have HIV or a life expectancy of less than 6 months may be eligible for this study. Screening tests include a complete physical examination and medical history. There will be a collection of about 8 tablespoons of blood for analysis of blood counts as well as liver, kidney, and thyroid function; a pregnancy test; an electrocardiogram (EKG) to measure electrical activity of the heartbeat; an echocardiogram (ECHO), which uses sound waves to evaluate heart function; wearing of a Holter monitor for 24 hours while the electrical activity of the heart is recorded; and a bone marrow biopsy. Patients should not receive any vaccines when taking alemtuzumab or for at least 12 months after the last dose. In addition, patients should not take the herbal supplements Echinacea purpurea or Usnea 2 weeks before beginning the study and during it.