CH is the disproportionate clonal expansion of blood stem cells and their progeny driven by leukemia-associated somatic mutations and is associated with an increased risk of hematologic cancers and ischemic cardiovascular disease. Reassuringly, the incidence and genetic drivers of CH, in either donors or recipients, did not seem to differ from that reported for unselected individuals of similar ages. Interestingly, the study also reports on the posttransplant behavior of 5 cases of donor-engrafted CH. This scenario uniquely captures the impact of the transplant procedure and 2 different hematopoietic environments on the behavior of the same CH clone. The authors report greater clonal expansion in recipients with donor-engrafted CH compared with the growth of the same founder clone in donors, thus highlighting important features of CH biology.