We reported recently that neonatal supplementation with 52 micromol vitamin A reduced infant mortality by 64%; acute side effects were limited to a 3% excess rate of a bulging fontanelle. The current study was conducted to identify developmental changes at 3 y of age associated with neonatal vitamin A supplementation or a bulging fontanelle. Children who had a bulging fontanelle (n = 91) and 432 children who had normal fontanelles after receiving vitamin A or placebo were evaluated with the Bayley Scales of Infant Development. Mean scores for the mental, psychomotor, and behavioral rating scale (BRS) plus 3 subscales of the BRS were not significantly different for treatment-fontanelle-specific groups. In regression models predicting each score, a bulging fontanelle had a small negative effect in all models; when 1 child who was injured from birth was removed from the analysis the effect of a bulging fontanelle was not significant in any model (P > or = 0.35). Vitamin A supplementation had a small beneficial effect on all developmental scores, which was significant for one of the BRS subscales (orientation-engagement) and also for a second (motor quality) when the outlier child was removed. Compared with children with normal fontanelles in the placebo group, children with a bulging fontanelle in the vitamin A group tended to grow less (-0.5 cm, P = 0.33), whereas those with normal fontanelles in the vitamin A group grew significantly more (0.68 cm, P < 0.05), over the first 3 y of life. This study provides no evidence that neonatal vitamin A supplementation is associated with biologically significant adverse growth or developmental sequelae.