Feeding human milk exclusively to the very-low-birth-weight infant may lead to insufficient intakes of protein and energy. Although the milk is therefore often supplemented with protein and additional calories, there is usually no prior information on its macronutrient composition. If such data were available, it would be possible to individualize the fortification of the milk. To find simple, rapid, and inexpensive methods of enriching it, we evaluated existing macronutrient assays of human milk. Thirty frozen samples of early human milk (3-20 days of lactation) were analyzed for contents of protein (Kjeldahl, Lowry, and Bio-Rad protein assays), fat (Folch, total lipids assay, and creamatocrit), and carbohydrates (lactose and orcinol assays). The methods were modified to minimize cost and time. From these data, we find it appropriate to recommend the use of the Lowry (or, alternatively, the Bio-Rad) protein assay, the total lipids assay, and the orcinol carbohydrate assay for reasonably accurate determinations of the protein and energy contents of human milk. Because the variation in the carbohydrate content of human milk is very small, a more simple alternative approach would be to include only an average carbohydrate value for an estimate of energy content. These low-cost methods can be used in all laboratories affiliated to neonatal units taking care of preterm infants. Such individualized fortification should serve to further improve the nutritional management of very-low-birth-weight infants.