Scientists have developed a 38-gene classifier that can accurately predict patients who are at risk of developing leukemia. Gene expression was assessed in CD34+ cells from patients who developed therapy-related myelodysplasia or acute myeloid leukemia (t-MDS/AML) after transplantation and compared the results with control patients who did not develop t-MDS/AML. In an independent cohort, this classifier accurately distinguished patients who developed t-MDS/AML from those who did not, indicating the use of this classifier for determining those at risk for this complication.