Postnatal change in insulin-like growth factor-1 (IGF-I) was studied longitudinally in 9 very low birth weight infants ( < 1,200 g, < 30 weeks at birth) who were receiving 85% or more of their nutrient intake via the parenteral route. There was no apparent relationship between IGF-I, nitrogen intake, energy intake, or nitrogen retention. In 6/9 infants IGF-I decreased with postnatal age. A low IGF-I may reflect the poor nutritional status and growth rate commonly seen in sick preterm infants.