The financing of the National Institute of Health (INSALUD) of Spain will soon be based on Diagnosis-Related Groups (DRGs). Knowledge of the real cost of different DRGs is fundamental to ensure adequate financing and to establish criteria for comparisons between centers. Our public health system has no data on the real cost of critically burned patients and their DRGs. This retrospective descriptive study was carried out in a Major Burns Unit (MBU) and included all patients admitted between January and December 1996. Real total cost of the care of critical burned patients, cost per patient, and cost per DRG related with critical burn patients were calculated for the study period. Financing by Weighed Care Units (WCU) was compared with real costs. The total cost of the care of critical burn patients was 346,298,872 Spanish pesetas and the cost per patient was 4,439,729 ptas. WCU financing was 322,021,616 ptas and 4,128,482 ptas, respectively. The DRG with the highest total cost was 458 (non-extensive burns with skin grafts, 106,372,016 ptas). The DRG with the highest average cost was 472 (extensive burns with surgical procedure, 5,401,119 ptas). The DRG with the highest cost per stay was 457 (extensive burns without surgical procedure, 404,683 ptas). For the first time in Spain, the cost of DRGs related with critical burn patients is described. This information is necessary for DRG-based allocation of funds and for establishing criteria to compare centers. The real cost of critical burn patients exceeded WCU financing.