Optimal strategy for total parenteral nutrition (TPN) administration is essential both in terms of clinical effectiveness and economic efficiency. The aim of the present economic analysis was to provide a systematic and comprehensive cost comparison of the application of three currently available TPN systems: Separate Bottles (SB), Hospital-Compounded Bags (HCB) and Three-Compartment Bags (TCB). Sixty patients, admitted to the Geneva University Hospital and requiring TPN, were randomly assigned to one of the three systems. Three standard TPN formulas were prescribed to meet the patients' protein energy needs. TPN-related activities of medical, nursing and pharmacy staff were timed for the 24 hours of TPN administration. Manpower, nutrient solutions and medical supplies costs were calculated on the basis of mean Swiss salaries and hospital prices. TCB was the least expensive TPN system. SB and HCB systems' application costs were 120 and 150% of TCB cost, respectively. All intersystems cost comparisons were statistically significant (ANOVA p < or = 0.01). SB system required more items and manipulations, resulting in higher nurses manpower cost. Pharmacy overhead cost due to compounding was responsible for the higher cost of HCB system. Detailed manpower data presented in this study allow for an estimation of TPN application costs in other hospitals, using local salaries, specific product prices and compounding costs.