OBJECTIVE: Vitamin A supplementation reduces bronchopulmonary dysplasia (BPD)/death in extremely low birth weight neonates. It was hypothesized that compared with the standard regimen of 5000 IU 3 times per week for 4 weeks, (1) a higher dose (10,000 IU 3 x per week) would increase serum retinol and retinol binding protein (RBP) and lower relative dose responses (RDR), and (2) once-per-week dosing (15,000 IU once per week) would lead to equivalent levels, RBP, and RDR. STUDY DESIGN: Extremely low birth weight neonates (n = 120) receiving O(2)/mechanical ventilation at 24 hours were randomly assigned to (1) standard, (2) higher dose, or (3) once-per-week regimens. Measures of vitamin A deficiency were serum retinol <20 microg/dL, RBP <2.5 mg/dL, and/or RDR >10% on day 28. BPD was defined as O(2)/mechanical ventilation at 36 weeks' postmenstrual age. RESULTS: Groups were similar at enrollment (median gestational age, 25 weeks; birth weight, 689 g). Possible toxicity was seen in <5%. The higher dose regimen did not increase retinol or RBP, decrease RDR, or improve outcomes. Infants in the once-per-week regimen had lower retinol levels and higher RDR without an effect on outcomes. CONCLUSIONS: Compared with the standard regimen, once-per-week dosing worsened, and higher doses did not reduce, vitamin A deficiency. Therefore, the standard regimen is recommended.