OBJECTIVES:  Parenteral nutrition (PN) is critical for neonatal care and for infants who are unable to tolerate oral or enteral feeding during this important growth period. PN for these populations is highly complex and involves a multidisciplinary approach. This study aims to assess the total cost of compounded PN therapy for neonates, infants, and children METHODS:   A cost-model was constructed to assess total costs of PN therapy including prescribing, compounding, and administration. This tool was piloted in 3 Belgian hospitals, with a total of 763 patients and 7,488 compounded bags annually. Data were collected via literature review and face-to-face interviews in 12 hospitals in 4 countries (Belgium, France, Germany, and UK) about resource-utilization and costs. The variable and fixed costs such as ingredients, supplies, equipment, staff-time were included. Overall costs of hospital PN-therapy were calculated from expenditures. Staff-time spent preparing PN was measured to determine personnel costs; bottom-up costing was used to assign a monetary value using published list-prices. RESULTS:    In these hospitals, 93% of all PN bags were compounded in-hospital (either in the pharmacy or in the ward), and 7% were industrially manufactured. The daily total cost of one bag of in-hospital compounded PN equaled €53.26 (weighted average by PN days) per neonate across all weight groups. Supplies accounted for 22% of total costs, ingredients 20% and wages 54%; 22 minutes of staff-time per PN was uniquely attributable to compounding, not including time required for prescribing and supplementation.  Average costs per bag using pharmacy compounding for children <2 yrs was €74.65, and for children 2-18 years €93.85, of which 54% were attributed to ingredients and 31% to wage-costs, respectively. CONCLUSIONS:   The data showed that a significant proportion of the total cost of PN was due to staff-time. Ready prepared PN could reduce staff-time spent on compounding for patient-related activities.