Despite a successful national salt iodinization programme, endemic goitre still persists in Iranian children. In a cross-sectional study in Arak the prevalence of goitre was 5.2% in a sample of 6520 primary-school children. Subsamples of 193 children with goitre and 151 healthy children were assessed for urinary iodine excretion, thyroid hormone profile, insulin-like growth factor-1 (IGF-1) and serum zinc. The mean urinary iodine levels of goitrous children and healthy children were 17.4 µg/dL and 15.3 µg/dL respectively, suggesting that iodine consumption was adequate. No significant differences were found between goitrous and healthy schoolchildren in mean levels of urinary iodine, serum IGF-1 or serum zinc. Other factors need be evaluated to explain the residual prevalence of goitre.