Iron plays a role in the regulation of dopaminergic activity. In the present study, nonanemic children with attention deficit hyperactivity disorder (ADHD) were evaluated with regard to heme and nonheme iron metabolism and the effect of short-term iron administration on behavior. The study group consisted of 14 boys aged 7-11 years. All first underwent testing to rule out other psychiatric and medical problems. The severity of the ADHD symptoms was determined by parent and teacher scores on the Connors Rating Scale. Thereafter, each patient received an iron preparation (Ferrocal), 5 mg/kg/day for 30 days. Blood samples were taken before and after drug administration. Results showed a significant increase in serum ferritin levels (from 25.9 +/- 9.2 to 44.6 +/- 18 ng/ml) and a significant decrease on the parents' Connors Rating Scale scores (from 17.6 +/- 4.5 to 12.7 +/- 5.4). There were no changes in other blood parameters or in the teachers' scores on the rating scale. The effect of iron supplementation on the behavioral and cognitive symptoms in noniron-deficient ADHD children merits further investigation using a placebo-controlled study.