Abnormalities in hepatic fatty acid metabolism are involved in various diseases. In order to clarify the use of 123I-15-(p-iodophenyl)-3(R,S)-methylpentadecanoic acid ([123I]BMIPP) for imaging hepatic fatty acid metabolism, we determined the hepatic distribution/metabolism of [125I]BMIPP in mice at various metabolic statuses induced by fasting, and compared the results with those of [1-(14)C]palmitic acid ([1-(14)C]PA). Fed or fasted (6, 12, and 24 hour-fasted) mice were intravenously injected with [125I]BMIPP or [1-(14)C]PA. Hepatic radioactivity was measured at 1 to 120 minutes after the injection (n = 5 to 15/time points), and radioactive lipid metabolites were analyzed by thin-layer chromatography (n = 3/time points). The areas under the curves (AUCs) were calculated. In mice given [125I]BMIPP, the hepatic radioactivity was increased with the fasting time (AUC: 35.1, 45.5, 57.6, and 59.0 [% injected dose (ID)/g/kg]▪min for fed, 6, 12, and 24 hour-fasted). Similar characteristic changes were observed in mice given [1-(14)C]PA (100.6, 101.0, 116.5, and 121.5 [%ID/g/kg]▪min). Metabolite analysis showed that the triglyceride-fraction was increased by fasting in both groups (5.7, 12.8, 32.0, and 37.9 [%ID/g/kg]▪min for [125I]BMIPP groups; 20.6, 39.2, 66.0, and 67.9 [%ID/g/kg]▪min for [1-(14)C]PA groups). Thus, [125I]BMIPP demonstrated the changes in hepatic fatty acid metabolism induced by fasting, indicating the potential of [123I]BMIPP for imaging hepatic fatty acid metabolism.