Primary　Cultured　rat　aortic　vascular　smooth　muscle　cells　(VSMCs)　were　exposed　to　different　intensities　of　low-frequency　electromagnetic　fields　(LFEMFs)　at　20,　40,　and　60　mT　for　different　time　periods　(10,　20,　and　30　minutes).　Furthermore,　osteopontin　(OPN)　mRNA　and　protein　expressions　were　determined　by　reverse　transcription-polymerase　chain　reaction　(RT-PCR)　and　Western　blotting,　respectively.　Matrix　metalloprotemase-2　(MMP-2)　activity　was　measured　using　gelatin　zymography.　The　results　showed　that　the　OPN　mRNA　and　protein　expressions　and　MMP-2　activity　of　VSMCs　were　inhibited　by　exposure　to　LFEMFs　of　different　intensities　in　a　dose-dependent　manner　(P　＜　0.05)　but　not　in　a　time-dependent　manner.　In　conclusion,　exposure　to　LFEMFs　of　appropriate　intensity　for　a　suitable　time　period　can　result　in　the　inhibition　of　the　OPN　expression　and　MMP-2　activity　of　VSMCs,　indicating　the　potential　prophylactic　and　therapeutic　effects　of　LFEMFs　on　restenosis　(RS)　following　percutaneous　coronary　intervention　(PCI).　(Int　Heart　J　2008;　49:　597-604)