The objective of this study is to validate an all-in-one defined daily dose (DDD) methodology for studying the utilization of total parenteral nutrition (TPN) with patient-linked data. Furthermore, the utilization of TPN in intensive-care patients is described. In a prospective survey, conducted from March to August 1992 on two intensive-care units, 47 patients using TPN were followed. Adapted ratios of prescribed daily dose (PDD) and DDD for amino acids, fat emulsion, and carbohydrates were 0.76±0.22, 0.69±0.30 and 1.07±0.23 (mean±SD), respectively. The ratio of the number of TPN DDD's to the number of TPN treatment days was 0.84±0.18. The prescription rate of TPN was 19.9 DDD/100 beddays, composed of 5.9 DDD/100 beddays for amino acids, 5.8 for fat emulsion, and 8.2 (or carbohydrates. It was shown that the proposed all-in-one DDD methodology can be used to describe the utilization of TPN and its components. The DDD's for amino acids, fat emulsion, and carbohydrates are valid for use in intensive-care patients.