mantle and hepatopancreas of hard clam were constructed with SMART cDNA Library Construction Kit. The libraries have a high titer of 2.10×10^{and 1.60×10respectively. The recombined efficiency of each cDNA library exceeded 95 %. The all insert sizes of intestine library were over 1 kband the insert sizes over 1 kb in the mantle and hepatopancreas libraries were over 87.5%. Atotal of 3 168 clones of the libraries were randomly picked and sequenced from the 5 ′end of the cDNAs using a M13 universal primerand 3 029 raw sequences of the ESTs were processed and then assembled into 1 796 unigene involving 306 contigs and 1 490 singletons. Blastx analysis showed that 696 unigenes235 for mantle and 245 for hepatopancreasEvalueG10 to genes with known or putative functions in GenBank.The sequences containing microsatellite DNA accounted for 3.1% of all ESTs indicating that SSR sequences were rich in the ESTs of hard clam.}