Parenteral nutrition (PN) is critical in neonatal and pediatric care for patients unable to tolerate enteral feeding. This study assessed the total costs of compounding PN therapy for neonates, infants and children. Face-to-face and telephone interviews were conducted in 12 hospitals across four European countries (Belgium, France, Germany and UK) to collect information on resources utilized to compound PN, including nutrients, staff time, equipment cost and supplies. A bottom-up cost model was constructed to assess total costs of PN therapy by assigning monetary values to the resource utilization using published list prices and interview data. A total of 49,922 PN bags per year were used to treat 4295 neonatal and pediatric patients among these hospitals. The daily total costs of one compounded PN bag for neonates in the 12 hospitals across the four countries equalled euro 55.16 (Belgium euro 53.26, France euro 46.23, Germany euro 64.05, UK Ł 37.43/\[euro]42.86). Overall, nutrients accounted for 25% of total costs, supplies 18%, wages 54% and equipment 3%. Average costs per bag for infants <2 year were euro 84.52 (euro 74.65 in Belgium, euro 83.84 in France, euro 92.70 in Germany and Ł 52.63/euro 60.26 in the UK), and for children 2-18 years euro 118.02 (euro 93.85 in Belgium, euro 121.35 in France, euro 124.54 in Germany and Ł 69.49/euro 79.56 in the UK), of which 63% is attributable to nutrients and 28% to wages. The data indicated that PN costs differ among countries and a major proportion was due to staff time (Ł 1=euro 1.144959).