Ten percent CBA/N-derived stem cells can correct the anemia of pyruvate kinase-deficient mice. Three million marrow cells from a mixture of CBA/N and CBA-Pk-1^slc/Pk-1^slc were transplanted into CBA/N mice that had undergone complete myeloablation with 1050 cGy radiation. The percentage of CBA/N cells in the transplanted cell dose is indicated in the inset to the right. Mice were then observed for 15 weeks to monitor the severity of the anemia. The top horizontal line represents the average RBC number for CBA/N mice (10.8 ± 1.7; n = 20), and the lower horizontal line represents the RBC number for CBA-Pk-1^slc/Pk-1^slc (5.4 ± 0.8; n = 20). Error bars show 1 standard deviation.