Vitamin A (retinol) deficiency is associated with impaired healing from lung injury in very-low-birth-weight (VLBW) neonates susceptible to bronchopulmonary dysplasia (BPD). Vitamin A supplementation from birth may ameliorate this adverse outcome. We hypothesized that plasma retinol-binding protein (RBP) response to vitamin A administration, which provides a dynamic measure to vitamin A status, might be useful for early recognition of vitamin A deficiency in VLBW neonates at risk for BPD. We prospectively studied 20 VLBW neonates (inclusion criteria: birth weight < 1300 g, gestational age < 30 weeks, need for supplemental oxygen and mechanical ventilation for > 24 h after birth) who were eligible to receive vitamin A supplementation. In addition to sequential assessment of vitamin A status, we measured plasma RBP just before and 3 and 6 h after an intramuscular injection of vitamin A (2000 IU/kg retinyl palmitate) on Postnatal Days 1, 7, 15, 21, 29, and 43. The percentage increase in plasma RBP (delta-RBP) was calculated. A high plasma delta-RBP value ( > 8%) is indicative of vitamin A deficiency. Based on pulmonary outcome, the infants were divided into two groups: BPD (n = 12) and No BPD (n = 8). Mean vitamin A intake ranged from 1414 to 2114 IU/kg/day and did not differ between infant groups. Mean plasma vitamin A concentration increased from baseline levels on Postnatal Day 1 to levels within the desired range of 1.05-2.10 mumol/liter (30.0-60.0 micrograms/dl) during supplementation period in both infant groups.(ABSTRACT TRUNCATED AT 250 WORDS)