Intravenous administration of ferrite particles may be useful as contrast agents for magnetic resonance (MR) imaging of the liver. We studied several sensitive biochemical parameters of hepatocellular function and toxicity in rats after intravenous ferrite injections to determine whether there was any evidence of iron-induced hepatotoxicity. Light microscopy and iron determinations were performed on the liver, spleen, lung, and kidney. Forty-eight hours after a massive (250 mg iron per kilogram) ferrite injection, liver, spleen, and lung nonheme iron concentrations were markedly increased. Microscopy showed this iron to be entirely in reticuloendothelial cells. Despite the large increase in hepatic iron concentration, we found no evidence of hepatic mitochondrial or microsomal lipid peroxidation or organelle dysfunction, sensitive biochemical indicators of iron-induced hepatocellular injury. At 10 to 11 weeks after administration of ferrite in smaller doses (30 mg iron per kilogram), results of all biochemical and morphologic studies were normal. Furthermore, quantitative iron determinations and microscopic studies suggest that ferrite particles may be partially degraded and that iron is cleared from the liver during a 3-month period. Because ferrite particles are taken up by reticuloendothelial cells, hepatocellular function is not impaired and iron-induced hepatocellular injury does not occur.