Antifreeze proteins(AFPs),which depress the freezing point of water below the melting point (producing a characteristic thermal hysteresis),are well known for their antifreeze activity in both fish and terrestrial arthropods, but have only recently been identified in plants. The discovery, biochemical characteristics and the role in freezing tolerance of plant AFPs have been reviewed. Furthermore, the general mechanism of depressing the freezing point of water of AFPs has been discussed. The discovery of AFPs intrinsically produced by frost-tolerant plant is very significant. Isolation and characterization of genes for AFPs may provide the targeting information essential for the successful transformation of freezing-sensitive crops and fruits with genes encoding AFPs.