Since there is a reported interrelationship between vitamin A and Fe metabolism, and with immunological response, the objective was to evaluate the effect of a single dose of vitamin A administered to preschool children, on Fe and vitamin A nutritional status, anaemia and phagocytic function of neutrophils, 30 d after supplementation. A total of eighty children (sixty-eight supplemented and twelve controls) were supplemented orally with 200 000 IU (60 mg) vitamin A, and evaluated for nutritional, haematological and immunological responses at the beginning of the study and 30 d after supplementation. Parameters studied included Hb, serum ferritin, retinol and Fe concentrations, transferrin saturation, IL-4, interferon-γ and phagocityc capacity of neutrophils using non-fluorescent latex microbeads. After supplementation there was a significant increase in Hb concentration (P = 0·03), mean corpuscular Hb concentration (P = 0·001) and serum retinol (P = 0·0078). Prevalences of anaemia and vitamin A deficiency decreased significantly from 17·6 % to 13·2 % and from 25 % to 13·2 %, respectively. Regarding phagocytic function, there was a significant increase in the number of microbeads engulfed by neutrophils (P < 0·05) and no significant changes in cytokine concentrations at 1 month after treatment. A single dose of 200 000 IU (60 mg) vitamin A administered orally to a group of preschool children with a high prevalence of vitamin A deficiency enhanced serum retinol and Hb concentrations, decreased the prevalence of anaemia and vitamin A deficiency and improved the constitutive phagocytic capacity of neutrophils. Vitamin A supplementation could help to decrease vitamin A deficiency, anaemia prevalence and to improve the innate immunity response in preschool children. The effects were obtained without Fe supplementation.