The therapeutic management of patients with idiopathic hemochromatosis (IH) implies the evaluation of excess hepatic iron. This work was undertaken to confirm the value of computed tomography for the assessment of liver iron overload in such patients and to evaluate this technique during the course of treatment by phlebotomy. The study included 24 patients with initially untreated IH and 7 patients previously treated by phlebotomy for 10 months to 7 years. Follow-up was obtained in 15 subjects. In patients with untreated IH, liver attenuation coefficient (LAC) was always markedly increased (92.4 ± 7.1 Hounsfield units) as compared with LAC of subjects with normal liver (60.2 ± 3.1 Hounsfield units) and that of patients with chronic liver disease (53.8 ± 4.8 Hounsfield units), and was found to be specific for liver iron overload. LAC decreased progressively during phlebotomy, and this diminution was correlated with the amount of mobilized iron (r = 0.79, p < 0.001); it returned to normal values only after complete removal of iron overload. LAC was closely correlated with liver iron concentration (r = 0.83, p < 0.001), better than usual biochemical parameters, especially serum ferritin (r = 0.70, p < 0.01). This study confirms that the determination of LAC on computed tomography provides a reliable index of hepatic iron stores in patients with IH, without requiring a liver biopsy, and shows that this noninvasive method is of particular interest for the follow-up of patients treated by phlebotomy.