There is a lack of multi-center cost-identification studies for hematopoietic cell transplantation (HCT). We used a single longitudinal administrative claims database representing a national, commercially insured population to evaluate the feasibility of identifying HCT recipients and to establish a cohort of autologous and allogeneic HCT recipients to study inpatient and outpatient direct medical costs from transplant hospitalization through first 100 days post-transplantation. Using ICD-9 procedure and diagnosis codes, we identified 3365 patients who had received their first transplant in the United States between 2007 and 2009 (autologous, 1678, allogeneic, 1320, graft source not specified, 367). The median 100-day total costs for autologous HCT were $99 899 (interquartile range (IQR), $73 914-140 555), and for allogeneic HCT were $203 026 (IQR, $141 742-316 426). The majority of costs (>75%) occurred during the initial transplant hospitalization for both autologous and allogeneic HCT recipients. Costs were greater among pediatric (<= 20years) compared with adult (>20 years) recipients and this difference was more pronounced with allogeneic HCT. Using a claims database representing a national HCT population, we highlight the high costs associated with autologous and allogeneic HCT. Our study lays the foundation for using claims data for future research on economic aspects of HCT. Bone Marrow Transplantation (2013) 48, 294-300; doi:10.1038/bmt.2012.133; published online 9 July 2012