Iron state was measured as part of the comprehensive assessment of 165 patients with cystic fibrosis. Of 127 patients, 41 (32%) had low serum ferritin concentrations and at least this proportion were iron deficiency. Iron state did not correlate with clinical score, radiological score, or results of sputum culture. There was no evidence that patients with iron deficiency were either in better or worse clinical condition than those with better iron stores.