The “Transfusion Requirements in Critical Care” study, published by Hebert et al in the New England Journal of Medicine in 1999 (NEJM 1999;340:409-17), is one of the most important studies in transfusion medicine in the last 50 years. The authors performed a randomized, prospective study dividing patients in the intensive care unit into those who received transfusions “liberally” (only with hemoglobin below 10.0 g/dL) and on a “restricted” basis (only with hemoglobin levels below 7.0 g/dL). The study showed that the restrictive transfusion strategy was at least as effective as the liberal, with significantly less in-house mortality in the restrictive group (with the exception of those with serious cardiac disease). This is one of the landmark studies in this field, and it is quoted often to help justify the use of lower thresholds for transfusion of red cells.