Red‐Cell Life Span in the Acute Rat Leukaemia L 5222

S ummary . The life span of red cells produced under leukaemic conditions has been measured in the experimental rat leukaemia, L 5222. Red cells in leukaemic donors were labelled by injection of 59 Fe and their survival studied over a period of 11 weeks after transfusion to normal recipients. No difference in potential life span or random destruction could be detected from similarly treated red cells from normal 59 Fe‐injected donors. It is concluded that the red cells produced during this leukaemia have no intrinsic defect.