Dr. Morton A. Levy, Chief Resident in Medicine, Jewish Hospital of St. Louis, and Instructor in Medicine, Washington University School of Medicine: A 61-year-old white woman was hospitalized on Nov 1, 1965, because of multiple subcutaneous hemorrhages. She was well until March 30, 1965, when she was first treated by her private physician with chloramphenicol (1 gm daily for three days) for a urinary tract infection. She was seen again on April 2 and administration of chloramphenicol was continued for another three days; the urinary tract symptoms disappeared. In June, urinary tract symptoms recurred, and another three-day course of chloramphenicol therapy was instituted. Several days after completing this third course of chloramphenicol therapy, the patient noted spontaneous bruising and ecchymoses on all extremities after minimal trauma. In July, the following laboratory values were obtained: hematocrit, 35%; hemoglobin, 11.4 gm/100 ml; white blood cell count, 5,450/ cu mm; and differential cell