We have previously shown that brain ferritin H expression, which has been associated with iron utilization, is developmentally regulated. Because retinoic acid (RA) regulates gene expression and is involved in cellular differentiation, we tested the hypothesis that RA regulates ferritin H during brain development and neuronal differentiation. RA, administered to rats on postnatal day 1, produced a 4-fold increase in brain ferritin H mRNA (p < 0.01) after 24 h. To examine whether RA-stimulated neuronal differentiation contributed to this up-regulation, ferritin and ferritin H mRNA were measured in human neuronal precursor cells (NTera-2, NT2) before and after 4-weeks of RA-stimulated differentiation into post-mitotic neurons. Differentiation resulted in a 2-fold increase in both ferritin and ferritin H mRNA (p < 0.05). Immunocytochemistry and Northern analysis showed significant elevations in ferritin expression that began as early as 24 h after RA treatment. While there was also a significant increase in the labile iron pool after RA treatment, this did not occur until 72 h. These data show that RA regulates ferritin H expression during rat brain development and neuronal differentiation and suggests a new role for RA in brain iron metabolism.