Nosocomial pneumonia is a common hospital infection extending the hospital stay as complication of an underlying disease. From the hospital’s perspective nosocomial pneumonia is an unfavourable disease, as reimbursement by the statutory health insurance is practically not concerned since the implementation of the new diagnosis related reimbursement system in Germany in 2004. Therefore, an efficient antimicrobial therapy is mandatory. A prospective cohort study investigated costs and effectiveness of treatment of nosocomial pneumonia with piperacillin/tazobactam (Tazobac®1, Wyeth Pharma GmbH) or meropenem (Meronem®1, AstraZeneca GmbH). The results were transferred to the implemented DRG-reimbursement modalities. The multicentre cohort study was conducted open-label and prospectively in German hospitals in 1999/2000. Patients suffering from nosocomial pneumonia and receiving treatment with piperacillin/tazobactam or meropenem were observed. There was no intervention regarding the physicians’ decision concerning diagnostic and therapeutic measures, as cost determination was predominant. Since the effectiveness of the two alternative treatment regimens was comparable, a cost-minimisation-analysis was performed. The costs incurred due to the prolongation of the hospital stay were calculated from the perspective of the German statutory health insurance funds and the hospital. As nosocomial pneumonia is a complication that occurs during the hospital stay, it does not represent a specific disease related group; thus, the costs incurred by the hospital and the health insurance funds were calculated by using common DRG examples. The analysis included 114 patients of the piperacillin/tazobactam cohort (PT) and 84 patients of the meropenem cohort (M). No significant differences concerning demographics or outcome of therapy were observed between the two cohorts. For the group of postoperative patients (97 pat., PT: 63, M: 34) the German DRG I03C (femoral neck fracture followed by total endoprosthesis) was assumed. Prolongation of the hospital stay of 8.43 days (PT) and 11.32 days (M), respectively, lead to an average additional reimbursement of € 124 in the PT-cohort (M-cohort € 258). From the hospitals’ perspective costs amounting to € 3,034 (PT) and € 4,076 (M) were calculated. For non-postoperative patients (101 pat., PT: 51, M: 50) the DRG F62B and F62A (congestive heart failure) were used. Prolongation of the hospital stay was 7.45 days (PT) and 6.55 days (M), respectively. The average additional reimbursement was € 62 for PT and € 0 for M. Compared to the additional reimbursement the costs from the hospitals’ perspective amounted to € 1.635 (PT) and € 1.465 (M). Comparing the perspectives of statutory health insurance funds and hospitals a redistribution of economic burden is demonstrated in the example of nosocomial pneumonia. Before the implementation of the DRG system, a prolongation of hospital stays was completely covered by the statutory health insurance funds; now, the hospitals have to take over most of the costs. Therefore, an efficient antimicrobial therapy of nosocomial pneumonia is important for the hospitals from an economical point of view. In this case, the combination piperacillin/tazobactam and meropenem represent comparable alternatives.