A　simple　and　sensitive　conductometric　irnmunosensor　for　detection　of　alpha-fetoprotein　(AFP)　was　designed　using　carbon　nanoparticles　as　labels.　The　immunosensing　probe　was　fabricated　by　means　of　the　immobilization　of　monoclonal　anti-AFP　primary　antibodies　on　an　interdigitated　conductometric　transducer,　while　the　detection　antibodies　were　prepared　using　nanocarbon-conjugated　horseradish　peroxidase-labeled　anti-AFP　(CNP-HRP-anti-AFP).　With　a　sandwich-type　immunoassay　format,　the　conjugated　CNP-HRP-anti-AFP　on　the　transducer　was　increased　with　the　increase　of　AFP　in　the　sample,　and　the　conductivity　of　the　immunosensor　was　decreased　in　the　H2O2-KI　system.　Under　optimal　conditions,　the　immunosensor　exhibited　a　wide　dynamic　range　of　0.1-500　ng/mL　with　a　detection　limit　of　50　pg/mL　AFP　at　3　sigma.　The　reproducibility　and　recovery　were　＜10%　and　83.9-112.3%,　respectively.　Interestingly,　45　clinical　serum　specimens　were　assayed　using　the　conductometric　immunosensor,　and　the　results　were　in　accordance　with　those　obtained　from　our　Clinical　Laboratory　using　Roche　2010　Electrochemiluminescent　Automatic　Analyzer.　(C)　2010　Elsevier　B.V.　All　rights　reserved.