Critically ill patients admitted to the intensive care unit often have anemia from one or more of a number of possible causes including blood loss due to surgery or injury, frequent blood sampling, chronic diseases such as kidney failure or cancer or treatments being received, such as chemotherapy. Although the common treatment for anemia is red blood cell transfusion, the current guidelines for blood transfusions for children are based on available information regarding transfusions in adults. Since many characteristics specific to critically ill children may affect the way in which they respond to anemia and transfusion, additional information is needed to better define guidelines for the prevention and treatment of anemia in critically ill children. This is a multi-center study to collect information regarding the management of anemia in critically ill children. Information needed to evaluate anemia, blood loss and transfusions will be collected from the patients' hospital records. No blood draws or procedures will be required by this survey and no medication will be supplied by the study Sponsor. Each patient's treating physician will be responsible for all decisions regarding his/her clinical care and treatment during the study. Approximately 1200 patients will be enrolled into this study, which is divided into 2 parts. During part 1, at least 400 patients who are newly admitted to the Pediatric Intensive Care Unit (PICU) will be enrolled, regardless of their length of stay in the PICU. During part 2, up to an additional 800 patients who are newly admitted into the PICU and have remained there for > = 48 hours at the time of entry into the study will be enrolled. Information for each patient will be collected for up to 28 days or until time of discharge from the hospital or death of the patient, whichever occurs first. Blood loss will be reported for each day the patient remains in the PICU; information regarding the treatment of anemia, including number and reasons for transfusions will be collected for a maximum of 28 days, regardless of the length of stay in the PICU. Information collected at the time of discharge from the hospital will include date of discharge and whether or not the patient is receiving mechanical assistance to breathe. Several possible hypotheses are being generated in this study: 1) Blood loss due to procedures and routine laboratory tests may be a major cause of anemia and transfusions in critically ill children; 2) Determining significant causes of anemia and blood transfusions in children will allow for better future treatment of anemia; and 3) Pediatric patients who receive blood transfusions have more days on a ventilator (a machine that helps patients who cannot breathe on their own), longer stays in the PICU and decreased organ function. Since the study involves only collection of information, no treatment will be required by the Sponsor and no medication will be supplied by the Sponsor.