A　simple　and　sensitive　conductometric　immunosensor　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　0.1-500ng/mL　with　a　detection　limit　of　50pg/mL　AFP　at　3σ.　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.　©　2010　Elsevier　B.V.