This cross-sectional project is part of an ongoing longitudinal observational study investigating the association of Wilm?s Tumor gene 1 (WT1) transcript levels and the clinical events that lead to relapse post-hematopoietic cell transplantation (HCT). According to the study protocol, each patient will have a series of blood draws, starting pre-HCT, and at specified time points post-HCT, until 3 years. To test the hypothesis that WT1 transcript levels predict disease progression/relapse, real time quantitative PCR (RT-qPCR) methods will be employed to measure WT1 transcript levels in a cohort of leukemia patients. For this cross-sectional study, we performed measurements of WT1 transcript levels in 10 patient samples. Increased levels of WT1 transcripts were detected in a peripheral blood (PB) sample from a patient who was further confirmed to have a disease relapse. Other 9 samples tested did not have high levels of WT1 transcripts and their future specimens will be evaluated for associations between WT1 transcript levels and clinical characteristics (relapse specifically) as part of the main longitudinal study.